C程序设计语言（第2版）

不念不忘少年蓝@ 2022-08-05 11:08 248阅读 0赞

C程序设计语言（第2版）

这儿有一篇写的很好的读后感：[http://www.cnblogs.com/xkfz007/articles/2566424.html][http_www.cnblogs.com_xkfz007_articles_2566424.html]

第1章 导言

1. 单词计数

![复制代码][copycode.gif]

\#include <stdio.h>                       
int main()\{  
     int c,nl,nw,nc,flag;  
    flag= 0;  
    nl=nw=nc= 0;  
     while((c=getchar())!=EOF)\{  
        ++nc;  
         if(c== ' \\n ')  
            nl++;  
         if(c== '   '||c== ' \\n '||c== ' \\t ')  
            flag= 0;  
         else  if(!flag)\{  
            flag= 1;  
            ++nw;  
        \}  
    \}  
    printf( " %3d %3d %3d\\n ",nl,nw,nc);  
     return  0;  
\}

![复制代码][copycode.gif]

![201208051119386901.png][]

2. 函数参数——传值调用

在C语言中，所有函数参数都是通过"值"传递的。也就是说，传递给被调用函数的参数值存放在临时变量中，而不是存放在原来的变量中。这与其他某些语言是不同的。比如，Fortran等语言是通过"引用"调用，Pascal则采用var参数方式，在这些语言中，被调用的函数必须访问原始参数，而不是访问参数的本地副本。

最主要的区别在于，在C语言中，被调用函数不能直接修改主调函数中变量的值，而只能修改其私有临时副本的值。

传值调用的利大于弊。在被调用该函数中，参数可以看作是便于初始化的局部变量，因此额外使用的变量更少。这样程序可以更紧凑简洁。

3. 读入一组文本，打印出最长文本

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
int getline\_( char s\[\], int lim)\{  
     int c,i;  
    i= 0;  
     while(i<lim- 1&&(c=getchar())!=EOF&&c!= ' \\n ')\{  
        s\[i++\]=c;  
    \}  
     if(c==EOF&&i== 0)  
         return - 1;  
     if(c== ' \\n ')  
        s\[i++\]=c;  
    s\[i++\]= ' \\0 ';  
     return i;  
\}  
void copy( char str1\[\], char str2\[\])\{  
     while((\*str1++=\*str2++)!= ' \\0 ');  
  
\}  
int main()\{  
     char line\[ 256\];  
     char longest\[ 256\];  
     char shortest\[ 256\];  
     int len;  
     int max= 0,min= 256;  
     while((len=getline\_(line, 256))>- 1)\{  
         if(len>=max)  
        \{  
            max=len;  
            copy(longest,line);  
        \}  
         else  if(len<=min)  
        \{  
            min=len;  
            copy(shortest,line);  
        \}  
    \}  
     if(max> 0)  
        printf( " %d:%s ",max,longest);  
     if(min< 256)  
        printf( " %d:%s ",min,shortest);  
     return  0;  
\}

![复制代码][copycode.gif]

下面是输出结果，输入是上面的源代码：

![201208051119395473.png][]

课后题程序：

习题1-8 编写一个统计空格、制表符和换行符个数的程序。

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
  int main()\{  
      int c,nb,nt,nl;  
     nb= 0;  
     nt= 0;  
     nl= 0;  
      while((c=getchar())!=EOF)\{  
          if(c== '   ')  
             nb++;  
          else  if(c== ' \\t ')  
             nt++;  
          else  if(c== ' \\n ')  
             nl++;  
     \}  
     printf( " %2d %2d %2d\\n ",nb,nt,nl);    
 \}

![复制代码][copycode.gif]

习题1-9 编写一个将输入复制到输出的程序，并将其中连续的多个空格使用一个空格代替

![复制代码][copycode.gif]

\#include <stdio.h>  
int main()\{  
     int c;  
     int nb;  
     int prec=- 1;  
     while((c=getchar())!=EOF)\{  
         if(c== '   '&&prec== '   ')  
             continue;  
         else                           
        \{  
            putchar(c);  
            prec=c;  
        \}  
    \}  
\}

![复制代码][copycode.gif]

习题1-12 编写一个程序，以每行一个单词的形式打印其输入

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

int main()\{  
     int c;  
     int flag;  
    flag= 0;  
     while((c=getchar())!=EOF)\{  
         if(c== '   '||c== ' \\n '||c== ' \\t ')\{  
             if(flag)\{  
                putchar( ' \\n ');  
                flag= 0;  
            \}  
        \}  
         else  if(!flag)\{  
            flag= 1;  
            putchar(c);  
        \}  
         else\{  
            putchar(c);  
        \}  
    \}  
\}

![复制代码][copycode.gif]

习题1-13 编写一个程序，打印输入中单词长度的直方图。水平方向的直方图比较容易绘制，垂直方向的直方图则要困难写。

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#define MAXHIST 15  
\#define MAXWORD 11  
int word\_stats( int wl\[\])\{  
     int flag;  
     int c,nc,i,ovflow;  
    flag= 0;  
    nc= 0;  
    ovflow= 0;  
     for(i= 0;i<MAXWORD;i++)  
        wl\[i\]= 0;  
     while((c=getchar())!=EOF)\{  
         if(c== '   '||c== ' \\n '||c== ' \\t ')\{  
             if(flag)\{  
                flag= 0;  
//                 if(nc>0)   
                 if(nc<MAXWORD)  
                    wl\[nc\]++;  
                 else  
                    ovflow++;  
                nc= 0;  
            \}  
        \}  
         else  if(!flag)\{  
            flag= 1;  
            nc= 1;  
        \}  
         else  
            nc++;  
    \}  
     return ovflow;  
\}  
void hist\_h( int wl\[\])\{  
     int i;  
     int maxvlaue= 0;  
     int len;  
     for(i= 1;i<MAXWORD;i++)  
         if(wl\[i\]>maxvlaue)  
            maxvlaue=wl\[i\];  
     for(i= 1;i<MAXWORD;++i)\{  
        printf( " %5d - %5d : ",i,wl\[i\]);  
         if(wl\[i\]> 0)\{  
             if((len=wl\[i\]\*MAXHIST/maxvlaue)<= 0)  
                len= 1;  
        \}  
         else  
            len= 0;  
         while(len> 0)\{  
            putchar( ' \* ');  
            len--;  
        \}  
        putchar( ' \\n ');  
    \}  
\}  
void hist\_v( int wl\[\])\{  
     int i,j;  
     int maxvlaue= 0;  
     int len;  
     for(i= 1;i<MAXWORD;i++)  
         if(wl\[i\]>maxvlaue)  
            maxvlaue=wl\[i\];  
     for(i=MAXHIST;i> 0;i--)\{  
         for(j= 1;j<MAXWORD;j++)  
             if(wl\[j\]\*MAXHIST/maxvlaue>=i)  
                printf( "    \*  ");  
             else  
                printf( "       ");  
        putchar( ' \\n ');  
    \}  
     for(i= 1;i<MAXWORD;i++)  
        printf( " %4d  ",i);  
    putchar( ' \\n ');  
     for(i= 1;i<MAXWORD;i++)  
        printf( " %4d  ",wl\[i\]);  
    putchar( ' \\n ');  
\}  
int main()\{  
     int wl\[MAXWORD\];  
     int ovflow;  
    ovflow=word\_stats(wl);  
    hist\_h(wl);  
    hist\_v(wl);  
     if(ovflow)  
        printf( " Overflow: %d\\n ",ovflow);  
\}

![复制代码][copycode.gif]

![201208051119394360.png][]

下面是以上面的源文件为输入得到的运行结果：

![201208051119391295.png][]

习题1-18 编写一个程序，删除每个输入行末尾的空格及制表符，并删除完全是空格的行

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
int getline\_( char s\[\], int lim)\{  
     int c;  
     int i;  
    i= 0;  
     while(i<lim- 1&&(c=getchar())!=EOF&&c!= ' \\n ')\{  
        s\[i++\]=c;  
    \}  
     if(c==EOF&&i== 0)  
         return - 1;  
     if(c== ' \\n ')  
        s\[i++\]=c;  
    s\[i++\]= ' \\0 ';  
     return i;  
\}  
int remove\_( char s\[\])\{  
     int i;  
    i= 0;  
     while(s\[i\]!= ' \\n ')  
        ++i;  
    --i;  
     while(i>= 0&&(s\[i\]== '   '||s\[i\]== ' \\t '))  
        --i;  
     if(i>= 0)\{  
        s\[++i\]= ' \\n ';  
        s\[++i\]= ' \\0 ';  
    \}  
     return i;  
\}  
int main()\{  
     char line\[ 256\];  
     while(getline\_(line, 256)> 0)\{                    
         if(remove\_(line)> 0)  
            printf( " %s ",line);  
    \}  
\}

![复制代码][copycode.gif]

习题1-19 编写函数rverse(s)将字符串s中的字符顺序颠倒过来。使用该函数编写一个程序，每次颠倒一个输入行中的字符顺序。

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
int getline\_( char s\[\], int lim)\{  
     int c;  
     int i;  
    i= 0;  
     while(i<lim- 1&&(c=getchar())!=EOF&&c!= ' \\n ')\{  
        s\[i++\]=c;  
    \}     
     if(c==EOF&&i== 0)  
         return - 1;  
     if(c== ' \\n ')  
        s\[i++\]=c;  
    s\[i++\]= ' \\0 ';  
     return i;  
\}     
void reverse\_( char s\[\])\{  
     int i,j;  
     char c;  
    i= 0;  
     while(s\[i\]!= ' \\0 ')  
        i++;  
    i--;  
     if(s\[i\]== ' \\n ')  
        i--;  
    j= 0;  
     while(j<i)\{  
        c=s\[i\];  
        s\[i\]=s\[j\];  
        s\[j\]=c;  
        j++;  
        i--;  
    \}  
\}  
int main()\{  
     char line\[ 256\];  
     while(getline\_(line, 256)> 0)\{  
        reverse\_(line);  
        printf( " %s ",line);                               
    \}  
\}

![复制代码][copycode.gif]

习题1-20

请编写程序detab，将输入中的制表符替换成适当数目的空格，使空格充满到下一个制表符终止的地方。假设制表符终止的位置是固定的，比如每隔n列就会出现一个制表符终止位。n应该作为变量还是常量呢？

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
  \#define TABINC 8  
  int main()\{  
      int c,nb,pos;  
     nb= 0;  
     pos= 1;  
      while((c=getchar())!=EOF)\{  
          if(c== ' \\t ')\{  
             nb=TABINC-(pos- 1)%TABINC;  
              while(nb> 0)\{  
                 putchar( '   ');  
                 pos++;  
                 nb--;  
             \}  
         \}    
          else  if(c== ' \\n ')\{  
             putchar(c);  
             pos= 1;  
         \}    
          else\{  
             putchar(c);  
             pos++;  
         \}  
     \}  
 \}

![复制代码][copycode.gif]

![201208051119396279.png][]

习题1-21 编写程序entab，将空格串替换为最少数量的制表符和空格，但要保持单词之间的间隔不变。假设制表符终止位的位置与练习1-20的detab程序的情况相同。当使用一个制表符或者一个空格都可以到达下一个制表符终止位时，选用那种替换字符比较好？

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#define TABINC 8  
int main()\{  
     int c,nb,nt,pos;  
    nb= 0;  
    nt= 0;  
    pos= 1;  
     while((c=getchar())!=EOF)\{  
         if(c== '   ')\{  
             if(pos%TABINC!= 0)  
                ++nb;  
             else\{  
                nb= 0;  
                nt++;  
            \}     
        \}     
         else\{  
             while(nt> 0)\{  
                putchar( ' \\t ');  
                nt--;  
            \}    
             if(c== ' \\t ')  
                nb= 0;  
             else  
                 while(nb> 0)\{  
                    putchar( '   ');  
                    nb--;  
                \}  
            putchar(c);  
             if(c== ' \\n ')  
                pos= 0;  
             else  if(c== ' \\t ')  
                pos=pos+(TABINC-(pos- 1)%TABINC)- 1;       
        \}  
          
        pos++;  
    \}  
\}

![复制代码][copycode.gif]

![201208051119394294.png][]

习题1-22

![201208051119405689.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#define MAXCOL 10  
\#define TABINC 8  
char line\[MAXCOL\];  
int exptab( int pos);  
int findblnk( int pos);  
int newpos( int pos);  
void printl( int pos);  
int main()\{  
     int c,pos;  
    pos= 0;  
     while((c=getchar())!=EOF)\{  
        line\[pos\]=c;  
         if(c== ' \\t ')  
            pos=exptab(pos);  
         else  if(c== ' \\n ') \{  
            printl(pos);  
            pos= 0;  
        \}  
         else  if(++pos>=MAXCOL)\{  
            pos=findblnk(pos);  
            printl(pos);  
            pos=newpos(pos);  
        \}  
    \}  
\}  
void printl( int pos)\{  
     int i;  
     for(i= 0;i<pos;i++)  
        putchar(line\[i\]);  
     if(pos> 0)  
        putchar( ' \\n ');  
\}  
int exptab( int pos)\{  
    line\[pos\]= '   ';  
     for(++pos;pos<MAXCOL&&pos%TABINC!= 0;++pos)  
        line\[pos\]= '   ';  
     if(pos<MAXCOL)  
         return pos;  
     else\{  
        printl(pos);  
         return  0;  
    \}  
\}  
int findblnk( int pos)\{  
     while(pos> 0&&line\[pos\]!= '   ')  
        pos--;  
     if(pos== 0)  
         return MAXCOL;  
     else  
         return pos+ 1;  
\}  
int newpos( int pos)\{  
     int i,j;  
     if(pos<= 0||pos>=MAXCOL)  
         return  0;  
     else\{  
        i= 0;  
         for(j=pos;j<MAXCOL;++j)\{  
            line\[i\]=line\[j\];  
            ++i;  
        \}  
         return i;  
    \}  
\}

![复制代码][copycode.gif]

![201208051119408164.png][]

习题1-23 编写一个删除C语言程序中所有的注释语句。要正确处理带银行的字符串与字符常量。在C语言中，注释不允许嵌套。

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
void rcomment( int c);  
void in\_comment( void);  
void echo\_quote( int c);  
int main()\{  
     int c;  
     while((c=getchar())!=EOF)  
        rcomment(c);  
     return  0;  
\}  
void rcomment( int c)\{  
     int d;  
     if(c== ' / ')  
         if((d=getchar())== ' \* ')  
            in\_comment();  
         else  if(d== ' / ')\{  
            putchar(c);  
            rcomment(d);  
        \}  
         else\{  
            putchar(c);  
            putchar(d);  
        \}  
     else  if(c== ' \\' '||c== ' " ')  
        echo\_quote(c);  
     else  
        putchar(c);  
\}  
void in\_comment( void)\{  
     int c,d;  
    c=getchar();  
    d=getchar();  
     while(c!= ' \* '||d!= ' / ')\{  
        c=d;  
        d=getchar();  
    \}  
\}  
void echo\_quote( int c)\{  
     int d;  
    putchar(c);  
     while((d=getchar())!=c)\{  
        putchar(d);  
         if(d== ' \\\\ ')  
            putchar(getchar());  
    \}  
    putchar(d);  
\}

![复制代码][copycode.gif]

![201208051119409768.png][]

习题1-24 编写一个程序，检查C语言程序中的基本语法错误

![201208051119401163.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
int brace,brack,paren;  
void in\_quote( int c);  
void in\_comment( void);  
void search( int c);  
int main()\{  
     int c;  
     while((c=getchar())!=EOF)\{  
         if(c== ' / ')\{  
             if((c=getchar())== ' \* ')  
                in\_comment();  
             else  
                search(c);  
        \}  
         else  if(c== ' \\' '||c== ' " ')  
            in\_quote(c);  
         else  
            search(c);  
         if(brace< 0)\{  
            printf( " Unbalanced braces\\n ");  
            brace= 0;  
        \}  
         else  if(brack< 0)\{  
            printf( " Unbalanced brackets\\n ");  
            brack= 0;  
        \}  
         else  if(paren< 0)\{  
            printf( " Unbalanced parentheses\\n ");  
            paren= 0;  
        \}  
    \}  
     if(brace> 0)  
        printf( " Unbalanced braces\\n ");  
     if(brack> 0)  
        printf( " Unbalanced brackets\\n ");  
     if(paren> 0)  
        printf( " Unbalanced parentheses\\n ");  
  
\}  
void search( int c)\{  
     if(c== ' \{  ')  
        ++brace;  
     else  if(c== ' \} ')  
        --brace;  
     else  if(c== ' \[ ')  
        ++brack;  
     else  if(c== ' \] ')  
        --brack;  
     else  if(c== ' ( ')  
        ++paren;  
     else  if(c== ' ) ')  
        --paren;  
\}  
void in\_comment( void)\{  
     int c,d;  
    c=getchar();  
    d=getchar();  
     while(c!= ' \* '||d!= ' / ')\{  
        c=d;  
        d=getchar();  
    \}  
\}  
void in\_quote( int c)\{  
     int d;  
     while((d=getchar())!=c)  
             if(d== ' \\\\ ')  
            getchar();  
\}

![复制代码][copycode.gif]

![201208051119414685.png][]

第2章 类型，运算符与表达式

1. const限定符

任何变量的声明都可以使用const限定符限定。该限定符指定变量的值不能被修改。对于数组而言，const限定符指定数组所有元素的值都不能被修改。

const char msg\[\]="warning:";

const限定符也可以配合数组参数使用，它表明函数不能修改该数组元素的值。

2. char类型

char类型是小整型

![201208051119413016.png][]

3. 算术中的隐式类型转换

一般情况下，如果不含有unsigned类型，可以采用下面的方式：

![201208051119428523.png][]

注意float类型的特殊性：

![201208051119429046.png][]

当表达式中含有unsigned类型时：

![201208051119425981.png][]

函数参数中的类型转换：

![20120805111942965.png][]

4. 标准库中的伪随机数发生器函数：rand和srand

标准库中包含一个可移植的实现伪随机数发生器的函数rand以及一个初始化种子数的函数srand。rand函数中使用了强制类型转换：

![复制代码][copycode.gif]

unsigned  long  int next= 1;  
/\* rand:return pseudo-random integer on 0..32767 \*/  
int rand( void)  
\{  
next=next\* 1103515245\+ 12345;  
return (unsigned  int)(next/ 65536)% 32768;  
\}  
/\* srand:set seed for rand() \*/  
void srand(unsigned  int seed)\{  
 next=seed;  
\}

![复制代码][copycode.gif]

习题2-3 编写函数htoi(s)，把由十六进制数字组成的字符串（包含可选的前缀0x或0X）转换为与之等价的整型数。字符串中允许包含的数字包括：0～9，a～f以及A-F

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
\#define YES 1  
\#define NO 0  
int htoi( char s\[\])\{  
     int hexd,i,inhex,n;  
    i= 0;  
     if(s\[i\]== ' 0 ')\{  
        ++i;  
         if(s\[i\]== ' x '||s\[i\]== ' X ')  
            ++i;  
    \}  
    n= 0;  
    inhex=YES;  
     while(inhex)\{  
         if(s\[i\]>= ' 0 '&&s\[i\]<= ' 9 ')  
            hexd=s\[i\]- ' 0 ';  
         else  if(s\[i\]>= ' a '&&s\[i\]<= ' f ')  
            hexd=s\[i\]- ' a '\+ 10;  
         else  if(s\[i\]>= ' A '&&s\[i\]<= ' F ')  
            hexd=s\[i\]- ' A '\+ 10;  
         else  
            inhex=NO;  
         if(inhex==YES)  
            n= 16\*n+hexd;  
        i++;  
    \}  
     return n;  
\}  
int main()\{  
     int count= 10;  
     int i;  
     char s\[ 100\];  
     for(i= 0;i< 10;i++)\{  
         int num=rand()% 10000;  
         int n;  
        sprintf(s, " %\#0x ",num);  
        n=htoi(s);                                       
        printf( " %\#0x %s %d %d \\n ",num,s,num,n);  
          
    \}  
      
\}

![复制代码][copycode.gif]

一个运行结果展示：

![20120805111942409.png][]

习题2-4 重写函数squeeze(s1,s2),将字符串s1中任何与字符串s2中字符匹配的字符都删除

![复制代码][copycode.gif]

void squeeze( char s1\[\], char s2\[\])\{  
     int i,j,k;  
     for(i=k= 0;s1\[i\]!= ' \\0 ';i++)\{  
         for(j= 0;s2\[j\]!= ' \\0 '&&s2\[j\]!=s1\[i\];j++);  
         if(s2\[j\]== ' \\0 ')  
            s1\[k++\]=s1\[i\];  
    \}  
    s1\[k\]= ' \\0 ';                                       
\}

![复制代码][copycode.gif]

![201208051119428424.png][]

习题2-5

![201208051119435359.png][]

![复制代码][copycode.gif]

void any( char s1\[\], char s2\[\])\{  
     int i,j;  
     for(i= 0;s1\[i\]!= ' \\0 ';i++)  
         for(j= 0;s2\[j\]!= ' \\0 ';j++)  
             if(s1\[i\]==s2\[j\])  
                 return i;  
     return - 1;                           
\}

![复制代码][copycode.gif]

5. C语言中的位操作

getbits函数：返回x中从右边数第p位开始向右数n位的字段。这里假定最右边的一位是第0位，n与p都是合理的正值。

unsigned getbits(unsigned x, int p, int n)\{  
      return (x>>(p+ 1\-n))&~(~ 0<<n);  
 \}

![20120805111943342.png][]

![复制代码][copycode.gif]

unsigned sebits(unsgined x, int p, int n,unsigned y)\{  
     unsigned x1=x&(~ 0<<(p+ 1)); // 获取x的高32-(p+1)位   
     unsigned x2=x&(( 1<<(p-n+ 1))- 1); // 获取x的低p-n+1位   
     unsigned y1=(y&~(~ 0<<n))<<(p+ 1\-n); // 获得y的最低n位，并且移动到合适的位置   
      return x1|x2|y1;  
 \}

![复制代码][copycode.gif]

可以换一种方式写：

![复制代码][copycode.gif]

unsigned sebits(unsgined x, int p, int n,unsigned y)\{  
     unsigned m1= (~ 0<<(p+ 1))| (( 1<<(p-n+ 1))- 1); // 得到屏蔽码   
unsigned x1=x&m1;  
     unsigned y1=(y&~(~ 0<<n))<<(p+ 1\-n); // 获得y的最低n位，并且移动到合适的位置   
      return x1|y1;  
 \}

![复制代码][copycode.gif]

下面是一个标准答案：

![20120805111944800.png][]

这儿比较难写是就是x的屏蔽码，下面的程序是对比两种方法产生的屏蔽码：

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
int main()\{  
     int i;  
     for(i= 0;i< 10;i++)\{  
         int p=rand()% 32;  
         int n=rand()%p+ 1;  
        unsigned m1=(~ 0<<(p+ 1))|(( 1<<(p-n+ 1))- 1);  
        unsigned m2=~(~(~ 0<<n)<<(p+ 1\-n));  
        printf( " p=%d n=%d: %\#0x %\#0x  ",p,n,m1,m2);        
         if(m1==m2)  
            printf( " OK\\n ");  
         else  
            printf( " NO\\n ");      
    \}  
\}

![复制代码][copycode.gif]

一个输出结果如下：

![20120805111944243.png][]

![201208051119445227.png][]

![复制代码][copycode.gif]

unsigned invert(unsigned x, int p, int n)\{  
     unsigned x1=x&(~ 0<<(p+ 1)); // 获取x的高32-(p+1)位   
     unsigned x2=x&(( 1<<(p-n+ 1))- 1); // 获取x的低p-n+1位   
     unsigned x3=~x&(~(~ 0<<n)<<(p-n+ 1)); // 获取x的中间n位   
      return x1|x2|x3;  
 \}

![复制代码][copycode.gif]

下面是一个标准答案

![201208051119443765.png][]

下面是一个测试：

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
unsigned invert(unsigned x, int p, int n)\{  
    unsigned m1=(~ 0<<(p+ 1)); // 获取x的高32-(p+1)位   
    unsigned x1=x&m1;  
    unsigned m2=(( 1<<(p-n+ 1))- 1); // 获取x的低p-n+1位   
    unsigned x2=x&m2;  
    unsigned m3=(~(~ 0<<n)<<(p-n+ 1)); // 获取x的中间n位   
    unsigned x3=(~x)&m3;  
    printf( " %\#0x %\#0x %\#0x\\n ",m1,m2,m3);  
     return x1|x2|x3;  
\}  
unsigned invert2(unsigned x, int p, int n)\{  
     return x^(~(~ 0<<n)<<(p+ 1\-n));  
\}  
int main()\{  
     int i;  
    unsigned x=rand();  
     for(i= 0;i< 25;i++)\{                                                    
         int p=rand()% 32;  
         int n=rand()%p+ 1;  
         int y1=invert(x,p,n);  
         int y2=invert2(x,p,n);  
        printf( " %\#0x %2d %2d %\#0x %\#0x  ",x,p,n,y1,y2);  
         if(y1==y2)  
            printf( " OK\\n ");  
         else  
            printf( " NO\\n ");  
  
    \}  
\}

![复制代码][copycode.gif]

输出如下：

![20120805111945701.png][]

可以看到当p=31时，第一种方法就出错了。主要是将一个无符号数进行右移32位（移出所有位）时，编译器会给出一个【 warning: right shift count >= width of type】的警告。然后返回原始值，而不是0

![201208051119457320.png][]

unsigned rightrot(unsigned x, int n)\{  
     unsigned x1=x>>n; // 左移得到高32-n位   
     unsigned x2=x<<( sizeof(x)\* 8\-n); // 右移得到低n位   
      return x1|x2;                                        
 \}

下面标准答案给出的解释：

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
int wordlength()  
\{                                           
     int i;  
    unsigned v=(unsigned)~ 0;  
     for(i= 1;(v=v>> 1)> 0;i++)  
        ;  
     return  1;  
\}         
unsigned rightrot(unsigned x, int n)\{  
     int rbit;  
     while(n--> 0)\{  
        rbit=(x& 1)<<(wordlength()- 1);  
        x=x>> 1;  
        x=x|rbit;  
    \}     
     return x;  
\}

![复制代码][copycode.gif]

![201208051119454256.png][]

![复制代码][copycode.gif]

unsigned rightrot2(unsigned x, int n)\{  
    unsigned rbits;  
     if((n-n%wordlength())> 0)\{  
        rbits=~(~ 0<<n)&x;  
        rbits=rbits<<(wordlength()-n);  
        x=x>>n;  
        x=x|rbits;  
    \}  
     return x;  
\}

![复制代码][copycode.gif]

![201208051119457811.png][]

6. 统计整型数中二进制位1的个数：

![复制代码][copycode.gif]

int bitcount(unsigned x)\{  
     int n= 0;  
     while(x!= 0)\{  
         if(x& 0x1)  
            n++;  
        x>> 1;  
    \}  
     return n;                    
\}

![复制代码][copycode.gif]

习题 2-9 在求对二的补码时，表达式x&(x-1)可以删除x中最右边为1的一个二进制位。请解释这样做的道理。用这一方法重写bitcount函数， 以加快其执行速度。

重写的代码如下：

![复制代码][copycode.gif]

int bitcount(unsigned x)\{  
     int b;  
    b= 0;  
     while(x!= 0)\{  
        b++;  
        x&=x- 1;  
    \}  
     return b;  
\}

![复制代码][copycode.gif]

![201208051119456698.png][]![201208051119466109.png][]

第3章 程序流控制

1. 折半查找

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

int bin\_search( int x, int v\[\], int n)\{  
     int low,high,mid;  
    low= 0;  
    high=n- 1;  
     while(low<=high)\{  
        mid=(low+high)>> 1;  
         if(x<v\[mid\])  
            high=mid- 1;  
         else  if(x>v\[mid\])  
            low=mid+ 1;  
         else  
             return mid;  
    \}  
     return - 1;  
\}  
  
int bin\_search( int x, int v\[\], int n)\{  
     int low,high,mid;  
    low= 0;  
    high=n- 1;  
    mid=(low+high)/ 2;  
     while(low<=high&&x!=v\[mid\])\{  
         if(x<v\[mid\])  
            high=mid- 1;  
         else  
            low=mid+ 1;  
        mid=(low+high)/ 2;  
    \}  
     if(x==v\[mid\])  
         return mid;  
     else  
         return - 1;                              
\}

![复制代码][copycode.gif]

![201208051119466076.png][]

2. atoi函数

字符串转换为对应数值的函数atoi

![ContractedBlock.gif][]

测试输出如下：

![201208051119462695.png][]

希尔排序shell

shell算法是D.L. Shell于1959年发明的，基本思想是：先比较近距离的元素，而不是像简单交换排序算法那样先比较相邻的元素。这样可以快速减少大量的无序情况，从而减轻后序的工作。被比较的元素之间的距离逐步减少，直到减少为1，这时编程了相邻元素的互换。

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
void shellsort( int v\[\], int n)\{  
     int gap,i,j,temp;  
     for(gap=n/ 2;gap> 0;gap/= 2)  
         for(i=gap;i<n;i++)  
             for(j=i-gap;j>= 0&&v\[j\]>v\[j+gap\];j-=gap)\{  
                temp=v\[j\];  
                v\[j\]=v\[j+gap\];  
                v\[j+gap\]=temp;  
            \}  
\}  
void print\_arr( int v\[\], int n)\{  
     int i;  
     for(i= 0;i<n;i++)  
        printf( " %4d ",v\[i\]);  
    printf( " \\n ");  
\}                                                            
int main()\{  
     int i;  
     for(i= 0;i< 10;i++)\{  
         int arr\[ 20\],j,b\[ 20\];  
         for(j= 0;j< 20;j++)  
        \{  
             int val=rand()% 1000;  
            arr\[j\]=val;  
            b\[j\]=val;  
        \}  
        printf( " before: ");  
        print\_arr(b, 20);  
        shellsort(arr, 20);  
        printf( " after : ");  
        print\_arr(arr, 20);  
    \}  
\}

![复制代码][copycode.gif]

测试输出如下：

![201208051119474614.png][]

习题 3-3 讲些函数expand(s1,s2),将字符串s1中类似于a-z一类的速记符号在字符串s2中扩展为等价的完整列表abc...xyz。该函数可以处理大小写字母和数字，并且可以处理a-b-c,a-z0-9与a-z等类似的情况。作为前导和尾随的字符原样复制。

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
void expand( char s1\[\], char s2\[\])\{  
     char c;  
     int i,j;  
    i= 0;  
    j= 0;   
     while((c=s1\[i++\])!= ' \\0 ')\{  
         if(s1\[i\]== ' \- '&&s1\[i+ 1\]>=c)\{  
            i++;  
             while(c<s1\[i\])  
                s2\[j++\]=c++;  
        \}  
         else  
            s2\[j++\]=c;  
    \}  
    s2\[j\]= ' \\0 ';                            
\}

![复制代码][copycode.gif]

![20120805111947993.png][]

函数itoa：将整型数转化为字符串

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
void itoa( int n, char s\[\])\{  
     int i,sign;  
     int x,y;  
     if((sign=n)< 0)  
        n=-n;  
    i= 0;                                            
     do\{  
        s\[i++\]=n% 10\+ ' 0 ';  
    \}  
     while((n/= 10)> 0);  
     if(sign< 0)  
        s\[i++\]= ' \- ';  
    s\[i\]= ' \\0 ';  
      
     for(x= 0,y=i- 1;x<y;x++,y--) \{  
         char c=s\[x\];  
        s\[x\]=s\[y\];  
        s\[y\]=c;  
    \}  
\}  
int atoi\_( char s\[\])\{  
     int i,n,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(n= 0;isdigit(s\[i\]);i++)  
        n= 10\*n+(s\[i\]- ' 0 ');  
     return sign\*n;  
\}  
int main()\{  
     int i;  
     char s\[ 20\];  
     for(i= 0;i< 10;i++)\{  
         int val=rand();  
         int d;  
        itoa(val,s);  
        d=atoi\_(s);  
  
        printf( " %12d %12s %12d  ",val,s,d);  
         if(val==d)  
            printf( " OK\\n ");  
         else  
            printf( " NO\\n ");  
    \}  
\}

![复制代码][copycode.gif]

测试结果如下：

![201208051119474025.png][]

习题3-4

![201208051119477056.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

void itoa2( int n, char s\[\])\{  
      int i,sign;  
      int x,y;  
     sign=n;  
     i= 0;  
      do\{  
         s\[i++\]= ABS(n% 10)+ ' 0 ';  
     \}  
      while((n/= 10)!= 0);  
      if(sign< 0)  
         s\[i++\]= ' \- ';  
     s\[i\]= ' \\0 ';  
       
      for(x= 0,y=i- 1;x<y;x++,y--) \{  
          char c=s\[x\];  
         s\[x\]=s\[y\];  
         s\[y\]=c;  
     \}  
 \}

![复制代码][copycode.gif]

![201208051119484515.png][]

习题 3-5 编写函数itob(n,s,b)，将整数n转换为以b为底的数，并将结果以字符的形式保存到字符串s中。例如，itob(n,s,16)把整数n格式化为十六进制整数保存在s中。

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#define ABS(x) ((x)<0?-(x):(x))  
void itob( int n, char s\[\], int b)\{  
     int i,j,sign;  
     int x,y;  
    sign=n;  
    i= 0;  
     do\{  
        j=ABS(n%b);  
        s\[i++\]=(j< 10)?j+ ' 0 ':j+ ' a '\- 10;  
    \}  
     while((n/=b)!= 0);  
     if(sign< 0)  
        s\[i++\]= ' \- ';  
    s\[i\]= ' \\0 ';  
     for(x= 0,y=i- 1;x<y;x++,y--) \{  
         char c=s\[x\];  
        s\[x\]=s\[y\];  
        s\[y\]=c;  
    \}  
\}  
void test\_10()\{  
     int i;  
     char s\[ 20\];  
     for(i= 0;i< 10;i++)\{  
         int val=rand();  
         int d;  
         if(val& 0x1)  
            val=-val;  
        itob(val,s, 10);  
        sscanf(s, " %d ",&d);  
  
        printf( " %12d %12s %12d  ",val,s,d);  
         if(val==d)  
            printf( " OK\\n ");  
         else  
            printf( " NO\\n ");  
    \}  
\}  
void test\_8()\{  
     int i;  
     char s\[ 20\];  
     for(i= 0;i< 10;i++)\{  
         int val=rand();  
         int d;  
         if(val& 0x1)  
            val=-val;  
        itob(val,s, 8);  
//         d=atoi\_(s);   
        sscanf(s, " %o ",&d);  
        printf( " %\#14o %14s %\#14o  ",val,s,d);  
         if(val==d)  
            printf( " OK\\n ");  
         else  
            printf( " NO\\n ");  
    \}  
\}  
void test\_16()\{  
     int i;  
     char s\[ 40\];  
     for(i= 0;i< 10;i++)\{  
         int val=rand();  
         int d;  
         if(val& 0x1)  
            val=-val;  
        itob(val,s, 16);  
        sscanf(s, " %x ",&d);  
        printf( " %\#14x %14s %\#14x  ",val,s,d);  
         if(val==d)  
            printf( " OK\\n ");  
         else  
            printf( " NO\\n ");  
    \}  
\}  
int main()\{  
    printf( " base-10\\n ");  
    test\_10();  
    printf( " =========================\\n ");  
    printf( " base-8\\n ");  
    test\_8();  
    printf( " =========================\\n ");  
    printf( " base-16\\n ");  
    test\_16();  
\}

![复制代码][copycode.gif]

![201208051119483402.png][]

我们在测试程序中进行8，10和16三种进制的测试。主要是C语言提供到这三种进制的转换，这样便于我们的测试。

测试结果如下：

![20120805111948338.png][]

函数trim：用于删除字符串尾部的空格、制表符与换行符。当发现最右边的字符为非空格符、非制表符、非换行符时，就使用break语句从循环中退出。

![复制代码][copycode.gif]

\#include <stdio.h>  
int trim( char s\[\])\{  
     int i;  
     for(i=strlen(s)- 1;i>= 0;i--)  
         if(s\[i\]!= '   '&&s\[i\]!= ' \\t '&&s\[i\]!= ' \\n ')  
             break;  
    s\[i+ 1\]= ' \\0 ';  
     return i;  
\}

![复制代码][copycode.gif]

第4章 函数与程序结构

1. 实现类似UNIX系统上的grep类似的功能：strindex

![201208051119482497.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
  \#define MAXLINE 1000  
  char pattern\[\]= " line ";                                         
  int getline\_( char line\[\], int lim)\{  
      int i,c;  
     i= 0;  
      while(i<lim- 1&&((c=getchar())!=EOF)&&c!= ' \\n ')  
         line\[i++\]=c;  
      if(c==EOF&&i== 0)  
          return - 1;  
      if(c== ' \\n ')  
         line\[i++\]=c;  
     line\[i\]= ' \\0 ';  
      return i;  
 \}  
  int strindex( char src\[\], char itm\[\])\{  
      int i,j;  
  //     int len1=strlen(src);  
  //     int len2=strlen(itm);   
      for(i= 0;src\[i\]!= ' \\0 ';i++)\{  
          int k;  
   
          for(j= 0,k=i;itm\[j\]!= ' \\0 '&&itm\[j\]==src\[k\];j++,k++);  
          if(itm\[j\]== ' \\0 ')  
              return i;  
     \}  
      return - 1;  
 \}  
  int main()\{  
      char line\[MAXLINE\];  
      int found= 0;  
      while(getline\_(line,MAXLINE)> 0)  
          if(strindex(line,pattern)>= 0)\{  
             printf( " %s ",line);  
             found++;  
         \}  
   
 \}

![复制代码][copycode.gif]

习题 4-1 编写函数strrindex(s,t),它返回字符串t在s中最右边出现的位置。如果s中不包含t，则返回-1

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

int strrindex( char s\[\], char t\[\])\{  
     int i,j;  
     int pos=- 1;  
     for(i= 0;s\[i\]!= ' \\0 ';i++)\{  
         int k;  
  
         for(j= 0,k=i;t\[j\]!= ' \\0 '&&t\[j\]==s\[k\];j++,k++);  
         if(t\[j\]== ' \\0 ')  
            pos=i;  
    \}  
     return pos;  
\}

![复制代码][copycode.gif]

![201208051119489432.png][]

![复制代码][copycode.gif]

int strrindex2( char s\[\], char t\[\])\{  
     int i,j;  
     int ls=strlen(s);  
     int lt=strlen(t);  
     for(i=ls-lt;i>= 0;i--)\{  
         int k;  
         for(j= 0,k=i;t\[j\]!= ' \\0 '&&t\[j\]==s\[k\];j++,k++);  
         if(t\[j\]== ' \\0 ')  
             return i;  
    \}  
     return - 1;  
\}

![复制代码][copycode.gif]

![201208051119496368.png][]

函数atof：将字符串转换为浮点数

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <ctype.h>  
double atof\_( char s\[\])\{  
     double val,power;  
     int i,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(val= 0.0;isdigit(s\[i\]);i++)  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
     if(s\[i\]== ' . ')  
        i++;  
     for(power= 1.0;isdigit(s\[i\]);i++)\{  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
        power\*= 10;  
    \}    
     return sign\*val/power;  
\}     
int main()\{  
     int i;  
     for(i= 0;i< 25;i++)\{  
         double val=rand()% 100000/ 100.0;  
         char s\[ 20\];  
         double val2;  
        sprintf(s, " %f ",val);  
        val2=atof\_(s);  
        printf( " %10.5f %12s %10.5f\\n ",val,s,val2);        
    \}  
\}

![复制代码][copycode.gif]

![201208051119491351.png][]

习题4-2 对atof函数进行扩充，使他可以处理形如：

123.45e-6

的科学表示法，其中浮点数后面可能会紧跟一个e或E以及一个指数（可能有正负号）。

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

double atof\_( char s\[\])\{  
     double val,power;  
     int i,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(val= 0.0;isdigit(s\[i\]);i++)  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
     if(s\[i\]== ' . ')  
        i++;  
     for(power= 1.0;isdigit(s\[i\]);i++)\{  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
        power\*= 10;  
    \}  
    val= sign\*val/power;  
     if(s\[i\]== ' e '||s\[i\]== ' E ')\{  
         int exp;  
        sign=(s\[++i\]== ' \- ')?- 1: 1;  
         if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
            i++;  
         for(exp= 0;isdigit(s\[i\]);i++)  
            exp= 10\*exp+(s\[i\]- ' 0 ');  
         if(sign)  
             while(exp--> 0)  
                val\*= 10;  
         else  
             while(exp--> 0)  
                val/= 10;  
    \}  
     return val;  
\}

![复制代码][copycode.gif]

![201208051119496335.png][]

4.3 外部变量

![201208051119494350.png][]

一个简单的计算器程序

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#if 1  
\#include <stdio.h>  
\#include <stdlib.h>  
\#include <ctype.h>  
\#define ABS(x) ((x)<0?-(x):(x))  
  
double atof\_( char s\[\])\{  
     double val,power;  
     int i,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(val= 0.0;isdigit(s\[i\]);i++)  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
     if(s\[i\]== ' . ')  
        i++;  
     for(power= 1.0;isdigit(s\[i\]);i++)\{  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
        power\*= 10;  
    \}  
    val= sign\*val/power;  
     if(s\[i\]== ' e '||s\[i\]== ' E ')\{  
         int exp;  
        sign=(s\[++i\]== ' \- ')?- 1: 1;  
         if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
            i++;  
         for(exp= 0;isdigit(s\[i\]);i++)  
            exp= 10\*exp+(s\[i\]- ' 0 ');  
         if(sign)  
             while(exp--> 0)  
                val\*= 10;  
         else  
             while(exp--> 0)  
                val/= 10;  
    \}  
     return val;  
\}  
  
\#define MAXVAL 1000  
int sp= 0;  
double val\[MAXVAL\];  
void push( double f)\{  
     if(sp<MAXVAL)  
        val\[sp++\]=f;  
     else  
        printf( " error:stack full\\n ");  
\}  
double pop( void)\{  
     if(sp> 0)  
         return val\[--sp\];  
     else  
        printf( " error:stack empty\\n ");  
     return  0.0;  
\}  
  
\#define BUFSIZE 100  
char buf\[BUFSIZE\];  
int bufp= 0;  
int getch( void)\{  
     return bufp> 0?buf\[--bufp\]:getchar();  
\}  
void ungetch( int c)\{  
     if(bufp>=BUFSIZE)  
        printf( " ungetch: too many characters\\n ");  
     else  
        buf\[bufp++\]=c;  
\}  
  
\#define MAXOP 1000  
\#define NUMBER '0'  
int getop( char s\[\])\{  
     int i,c;  
     while((s\[ 0\]=c=getch())== '   '||c== ' \\t ')  
        ;  
    s\[ 1\]= ' \\0 ';  
     if(!isdigit(c)&&c!= ' . ')  
         return c;  
    i= 0;  
     if(isdigit(c))  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
     if(c== ' . ')  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
    s\[i\]= ' \\0 ';  
     if(c!=EOF)  
        ungetch(c);  
     return NUMBER;  
\}  
  
int main()\{  
     int type;  
     double op2;  
     char s\[MAXOP\];  
     while((type=getop(s))!=EOF)\{  
         switch(type)\{  
             case NUMBER:  
                push(atof\_(s));  
                 break;  
             case  ' \+ ':  
                push(pop()+pop());  
                 break;  
             case  ' \- ':  
                op2=pop();  
                push(pop()-op2);  
                 break;  
             case  ' \* ':  
                push(pop()\*pop());  
                 break;  
             case  ' / ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(pop()/op2);  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
             case  ' \\n ':  
                printf( " \\t%.8g\\n ",pop());  
                 break;  
             default:  
                printf( " error: unknown command %s\\n ",s);  
                 break;  
        \}  
    \}  
\}

![复制代码][copycode.gif]

![201208051119501809.png][]

![201208051119503204.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
\#include <ctype.h>  
\#include <math.h>  
\#define ABS(x) ((x)<0?-(x):(x))  
  
double atof\_( char s\[\])\{  
     double val,power;  
     int i,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(val= 0.0;isdigit(s\[i\]);i++)  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
     if(s\[i\]== ' . ')  
        i++;  
     for(power= 1.0;isdigit(s\[i\]);i++)\{  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
        power\*= 10;  
    \}  
    val= sign\*val/power;  
     if(s\[i\]== ' e '||s\[i\]== ' E ')\{  
         int exp;  
        sign=(s\[++i\]== ' \- ')?- 1: 1;  
         if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
            i++;  
         for(exp= 0;isdigit(s\[i\]);i++)  
            exp= 10\*exp+(s\[i\]- ' 0 ');  
         if(sign)  
             while(exp--> 0)  
                val\*= 10;  
         else  
             while(exp--> 0)  
                val/= 10;  
    \}  
     return val;  
\}  
  
\#define MAXVAL 1000  
int sp= 0;  
double val\[MAXVAL\];  
void push( double f)\{  
     if(sp<MAXVAL)  
        val\[sp++\]=f;  
     else  
        printf( " error:stack full\\n ");  
\}  
double pop( void)\{  
     if(sp> 0)  
         return val\[--sp\];  
     else  
        printf( " error:stack empty\\n ");  
     return  0.0;  
\}  
  
\#define BUFSIZE 100  
char buf\[BUFSIZE\];  
int bufp= 0;  
int getch( void)\{  
     return bufp> 0?buf\[--bufp\]:getchar();  
\}  
void ungetch( int c)\{  
     if(bufp>=BUFSIZE)  
        printf( " ungetch: too many characters\\n ");  
     else  
        buf\[bufp++\]=c;  
\}  
  
\#define MAXOP 1000  
\#define NUMBER '0'  
int getop( char s\[\])\{  
     int i,c;  
     while((s\[ 0\]=c=getch())== '   '||c== ' \\t ')  
        ;  
    s\[ 1\]= ' \\0 ';  
     if(!isdigit(c)&&c!= ' . '&&c!= ' \- ')  
         return c;  
    i= 0;  
     if(c== ' \- ')  
         if(isdigit(c=getch())||c== ' . ')  
            s\[++i\]=c;  
         else  
        \{  
             if(c!=EOF)  
                ungetch(c);  
             return  ' \- ';  
        \}  
     if(isdigit(c))  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
     if(c== ' . ')  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
    s\[i\]= ' \\0 ';  
     if(c!=EOF)  
        ungetch(c);  
     return NUMBER;  
\}  
  
int main()\{  
     int type;  
     double op2;  
     char s\[MAXOP\];  
     while((type=getop(s))!=EOF)\{  
         switch(type)\{  
             case NUMBER:  
                push(atof\_(s));  
                 break;  
             case  ' \+ ':  
                push(pop()+pop());  
                 break;  
             case  ' \- ':  
                op2=pop();  
                push(pop()-op2);  
                 break;  
             case  ' \* ':  
                push(pop()\*pop());  
                 break;  
             case  ' / ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(pop()/op2);  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
             case  ' % ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(fmod(pop(),op2));  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
  
             case  ' \\n ':  
                printf( " \\t%.8g\\n ",pop());  
                 break;  
             default:  
                printf( " error: unknown command %s\\n ",s);  
                 break;  
        \}  
    \}  
\}

![复制代码][copycode.gif]

![201208051119501776.png][]

![201208051119504807.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
\#include <ctype.h>  
\#include <math.h>  
\#define ABS(x) ((x)<0?-(x):(x))  
  
double atof\_( char s\[\])\{  
     double val,power;  
     int i,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(val= 0.0;isdigit(s\[i\]);i++)  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
     if(s\[i\]== ' . ')  
        i++;  
     for(power= 1.0;isdigit(s\[i\]);i++)\{  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
        power\*= 10;  
    \}  
    val= sign\*val/power;  
     if(s\[i\]== ' e '||s\[i\]== ' E ')\{  
         int exp;  
        sign=(s\[++i\]== ' \- ')?- 1: 1;  
         if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
            i++;  
         for(exp= 0;isdigit(s\[i\]);i++)  
            exp= 10\*exp+(s\[i\]- ' 0 ');  
         if(sign)  
             while(exp--> 0)  
                val\*= 10;  
         else  
             while(exp--> 0)  
                val/= 10;  
    \}  
     return val;  
\}  
  
\#define MAXVAL 1000  
int sp= 0;  
double val\[MAXVAL\];  
void push( double f)\{  
     if(sp<MAXVAL)  
        val\[sp++\]=f;  
     else  
        printf( " error:stack full\\n ");  
\}  
double pop( void)\{  
     if(sp> 0)  
         return val\[--sp\];  
     else  
        printf( " error:stack empty\\n ");  
     return  0.0;  
\}  
void clear( void)\{  
    sp= 0;  
\}  
  
\#define BUFSIZE 100  
char buf\[BUFSIZE\];  
int bufp= 0;  
int getch( void)\{  
     return bufp> 0?buf\[--bufp\]:getchar();  
\}  
void ungetch( int c)\{  
     if(bufp>=BUFSIZE)  
        printf( " ungetch: too many characters\\n ");  
     else  
        buf\[bufp++\]=c;  
\}  
  
\#define MAXOP 1000  
\#define NUMBER '0'  
int getop( char s\[\])\{  
     int i,c;  
     while((s\[ 0\]=c=getch())== '   '||c== ' \\t ')  
        ;  
    s\[ 1\]= ' \\0 ';  
     if(!isdigit(c)&&c!= ' . '&&c!= ' \- ')  
         return c;  
    i= 0;  
     if(c== ' \- ')  
         if(isdigit(c=getch())||c== ' . ')  
            s\[++i\]=c;  
         else  
        \{  
             if(c!=EOF)  
                ungetch(c);  
             return  ' \- ';  
        \}  
     if(isdigit(c))  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
     if(c== ' . ')  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
    s\[i\]= ' \\0 ';  
     if(c!=EOF)  
        ungetch(c);  
     return NUMBER;  
\}  
  
int main()\{  
     int type;  
     double op1,op2;  
     char s\[MAXOP\];  
     while((type=getop(s))!=EOF)\{  
         switch(type)\{  
             case NUMBER:  
                push(atof\_(s));  
                 break;  
             case  ' \+ ':  
                push(pop()+pop());  
                 break;  
             case  ' \- ':  
                op2=pop();  
                push(pop()-op2);  
                 break;  
             case  ' \* ':  
                push(pop()\*pop());  
                 break;  
             case  ' / ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(pop()/op2);  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
             case  ' % ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(fmod(pop(),op2));  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
             case  ' ? ':  
                op2=pop();  
                printf( " \\t%.8g\\n ",op2);  
                push(op2);  
                 break;  
             case  ' c ':  
                clear();  
                 break;  
             case  ' d ':  
                op2=pop();  
                push(op2);  
                push(op2);  
                 break;  
             case  ' s ':  
                op1=pop();  
                op2=pop();  
                push(op1);  
                push(op2);  
             case  ' \\n ':  
                printf( " \\t%.8g\\n ",pop());  
                 break;  
             default:  
                printf( " error: unknown command %s\\n ",s);  
                 break;  
        \}  
    \}  
\}

![复制代码][copycode.gif]

![201208051119507598.png][]

![201208051119502582.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
\#include <ctype.h>  
\#include <math.h>  
\#include < string.h>  
\#define ABS(x) ((x)<0?-(x):(x))  
  
double atof\_( char s\[\])\{  
     double val,power;  
     int i,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(val= 0.0;isdigit(s\[i\]);i++)  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
     if(s\[i\]== ' . ')  
        i++;  
     for(power= 1.0;isdigit(s\[i\]);i++)\{  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
        power\*= 10;  
    \}  
    val= sign\*val/power;  
     if(s\[i\]== ' e '||s\[i\]== ' E ')\{  
         int exp;  
        sign=(s\[++i\]== ' \- ')?- 1: 1;  
         if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
            i++;  
         for(exp= 0;isdigit(s\[i\]);i++)  
            exp= 10\*exp+(s\[i\]- ' 0 ');  
         if(sign)  
             while(exp--> 0)  
                val\*= 10;  
         else  
             while(exp--> 0)  
                val/= 10;  
    \}  
     return val;  
\}  
  
\#define MAXVAL 1000  
int sp= 0;  
double val\[MAXVAL\];  
void push( double f)\{  
     if(sp<MAXVAL)  
        val\[sp++\]=f;  
     else  
        printf( " error:stack full\\n ");  
\}  
double pop( void)\{  
     if(sp> 0)  
         return val\[--sp\];  
     else  
        printf( " error:stack empty\\n ");  
     return  0.0;  
\}  
  
\#define BUFSIZE 100  
char buf\[BUFSIZE\];  
int bufp= 0;  
int getch( void)\{  
     return bufp> 0?buf\[--bufp\]:getchar();  
\}  
void ungetch( int c)\{  
     if(bufp>=BUFSIZE)  
        printf( " ungetch: too many characters\\n ");  
     else  
        buf\[bufp++\]=c;  
\}  
  
  
void mathfnc( char s\[\])\{  
     double op2;  
     if(strcmp(s, " sin ")== 0)  
        push(sin(pop()));  
     else  if(strcmp(s, " cos ")== 0)  
        push(cos(pop()));  
     else  if(strcmp(s, " exp ")== 0)  
        push(exp(pop()));  
     else  if(strcmp(s, " pow ")== 0) \{  
        op2=pop();  
        push(pow(pop(),op2));  
    \}  
     else  
        printf( " error: %s not supported\\n ",s);  
\}  
  
\#define MAXOP 1000  
\#define NUMBER '0'  
\#define NAME 'n'  
int getop( char s\[\])\{  
     int i,c;  
     while((s\[ 0\]=c=getch())== '   '||c== ' \\t ')  
        ;  
    s\[ 1\]= ' \\0 ';  
    i= 0;  
     if(islower(c))\{  
         while(islower(s\[++i\]=c=getch()))  
            ;  
        s\[i\]= ' \\0 ';  
         if(c!=EOF)  
            ungetch(c);  
         if(strlen(s)> 1)  
             return NAME;  
         else   
             return c;  
    \}  
     if(!isdigit(c)&&c!= ' . '&&c!= ' \- ')  
         return c;  
     if(c== ' \- ')  
         if(isdigit(c=getch())||c== ' . ')  
            s\[++i\]=c;  
         else  
        \{  
             if(c!=EOF)  
                ungetch(c);  
             return  ' \- ';  
        \}  
     if(isdigit(c))  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
     if(c== ' . ')  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
    s\[i\]= ' \\0 ';  
     if(c!=EOF)  
        ungetch(c);  
     return NUMBER;  
\}  
  
int main()\{  
     int type;  
     double op1,op2;  
     char s\[MAXOP\];  
     while((type=getop(s))!=EOF)\{  
         switch(type)\{  
             case NUMBER:  
                push(atof\_(s));  
                 break;  
             case NAME:  
                mathfnc(s);  
                 break;  
             case  ' \+ ':  
                push(pop()+pop());  
                 break;  
             case  ' \- ':  
                op2=pop();  
                push(pop()-op2);  
                 break;  
             case  ' \* ':  
                push(pop()\*pop());  
                 break;  
             case  ' / ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(pop()/op2);  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
             case  ' % ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(fmod(pop(),op2));  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
             case  ' \\n ':  
                printf( " \\t%.8g\\n ",pop());  
                 break;  
             default:  
                printf( " error: unknown command %s\\n ",s);  
                 break;  
        \}  
    \}  
\}

![复制代码][copycode.gif]

![201208051119517216.png][]

![201208051119518612.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
\#include <ctype.h>  
\#include <math.h>  
\#define ABS(x) ((x)<0?-(x):(x))  
  
double atof\_( char s\[\])\{  
     double val,power;  
     int i,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(val= 0.0;isdigit(s\[i\]);i++)  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
     if(s\[i\]== ' . ')  
        i++;  
     for(power= 1.0;isdigit(s\[i\]);i++)\{  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
        power\*= 10;  
    \}  
    val= sign\*val/power;  
     if(s\[i\]== ' e '||s\[i\]== ' E ')\{  
         int exp;  
        sign=(s\[++i\]== ' \- ')?- 1: 1;  
         if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
            i++;  
         for(exp= 0;isdigit(s\[i\]);i++)  
            exp= 10\*exp+(s\[i\]- ' 0 ');  
         if(sign)  
             while(exp--> 0)  
                val\*= 10;  
         else  
             while(exp--> 0)  
                val/= 10;  
    \}  
     return val;  
\}  
  
\#define MAXVAL 1000  
int sp= 0;  
double val\[MAXVAL\];  
void push( double f)\{  
     if(sp<MAXVAL)  
        val\[sp++\]=f;  
     else  
        printf( " error:stack full\\n ");  
\}  
double pop( void)\{  
     if(sp> 0)  
         return val\[--sp\];  
     else  
        printf( " error:stack empty\\n ");  
     return  0.0;  
\}  
  
\#define BUFSIZE 100  
char buf\[BUFSIZE\];  
int bufp= 0;  
int getch( void)\{  
     return bufp> 0?buf\[--bufp\]:getchar();  
\}  
void ungetch( int c)\{  
     if(bufp>=BUFSIZE)  
        printf( " ungetch: too many characters\\n ");  
     else  
        buf\[bufp++\]=c;  
\}  
  
\#define MAXOP 1000  
\#define NUMBER '0'  
int getop( char s\[\])\{  
     int i,c;  
     while((s\[ 0\]=c=getch())== '   '||c== ' \\t ')  
        ;  
    s\[ 1\]= ' \\0 ';  
     if(!isdigit(c)&&c!= ' . '&&c!= ' \- ')  
         return c;  
    i= 0;  
     if(c== ' \- ')  
         if(isdigit(c=getch())||c== ' . ')  
            s\[++i\]=c;  
         else  
        \{  
             if(c!=EOF)  
                ungetch(c);  
             return  ' \- ';  
        \}  
     if(isdigit(c))  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
     if(c== ' . ')  
         while(isdigit(s\[++i\]=c=getch()))  
            ;  
    s\[i\]= ' \\0 ';  
     if(c!=EOF)  
        ungetch(c);  
     return NUMBER;  
\}  
  
int main()\{  
     int type,i, var= 0;  
     double op2, v;  
     char s\[MAXOP\];  
     double variable\[ 26\];  
     for(i= 0;i< 26;i++)  
        variable\[i\]= 0.0;  
      
     while((type=getop(s))!=EOF)\{  
         switch(type)\{  
             case NUMBER:  
                push(atof\_(s));  
                 break;  
             case  ' \+ ':  
                push(pop()+pop());  
                 break;  
             case  ' \- ':  
                op2=pop();  
                push(pop()-op2);  
                 break;  
             case  ' \* ':  
                push(pop()\*pop());  
                 break;  
             case  ' / ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(pop()/op2);  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
             case  ' % ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(fmod(pop(),op2));  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
  
             case  ' \\n ':  
                v=pop();  
                printf( " \\t%.8g\\n ",v);  
                 break;  
             case  ' = ':  
                pop();  
                 if( var>= ' A '&& var<= ' Z ')  
                    variable\[ var\- ' A '\]=pop();  
                 else  
                    printf( " error: no variable name\\n ");  
                 break;  
             default:  
                 if(type>= ' A '&&type<= ' Z ')  
                    push(variable\[type- ' A '\]);  
                 else  if(type == ' v ')  
                    push(v);  
                 else  
                    printf( " error: unknown command %s\\n ",s);  
                 break;  
        \}  
         var=type;  
    \}  
\}

![复制代码][copycode.gif]

![201208051119514675.png][]

![201208051119512483.png][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include < string.h>  
\#define BUFSIZE 100  
char buf\[BUFSIZE\];  
int bufp= 0;  
int getch( void)\{  
     return bufp> 0?buf\[--bufp\]:getchar();  
\}  
void ungetch( int c)\{  
     if(bufp>=BUFSIZE)  
        printf( " ungetch: too many characters\\n ");  
     else  
        buf\[bufp++\]=c;  
\}  
void ungets( char s\[\])\{  
     int len=strlen(s);  
     while(len> 0)  
        ungetch(s\[--len\]);  
\}

![复制代码][copycode.gif]

![201208051119523006.png][]

![201208051119526038.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

char buf= 0;  
int getch( void)\{  
     int c;  
     if(buf!= 0)  
        c=buf;  
     else  
        c=getchar();  
    buf= 0;  
     return c;  
\}    
void ungetch( int c)\{  
     if(buf!= 0)  
        printf( " ungetch:too many characters\\n ");  
     else  
        buf=c;                                      
\}

![复制代码][copycode.gif]

![201208051119529069.png][]

![201208051119536495.png][]

![201208051119537890.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
\#include <ctype.h>  
\#include <math.h>  
\#define ABS(x) ((x)<0?-(x):(x))  
  
double atof\_( char s\[\])\{  
     double val,power;  
     int i,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(val= 0.0;isdigit(s\[i\]);i++)  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
     if(s\[i\]== ' . ')  
        i++;  
     for(power= 1.0;isdigit(s\[i\]);i++)\{  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
        power\*= 10;  
    \}  
    val= sign\*val/power;  
     if(s\[i\]== ' e '||s\[i\]== ' E ')\{  
         int exp;  
        sign=(s\[++i\]== ' \- ')?- 1: 1;  
         if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
            i++;  
         for(exp= 0;isdigit(s\[i\]);i++)  
            exp= 10\*exp+(s\[i\]- ' 0 ');  
         if(sign)  
             while(exp--> 0)  
                val\*= 10;  
         else  
             while(exp--> 0)  
                val/= 10;  
    \}  
     return val;  
\}  
  
\#define MAXVAL 1000  
int sp= 0;  
double val\[MAXVAL\];  
void push( double f)\{  
     if(sp<MAXVAL)  
        val\[sp++\]=f;  
     else  
        printf( " error:stack full\\n ");  
\}  
double pop( void)\{  
     if(sp> 0)  
         return val\[--sp\];  
     else  
        printf( " error:stack empty\\n ");  
     return  0.0;  
\}  
  
// \#define BUFSIZE 100  
 // char buf\[BUFSIZE\];  
 // int bufp=0;  
 // int getch(void)\{  
 //     return bufp>0?buf\[--bufp\]:getchar();  
 // \}  
 // void ungetch(int c)\{  
 //     if(bufp>=BUFSIZE)  
 //         printf("ungetch: too many characters\\n");  
 //     else  
 //         buf\[bufp++\]=c;  
 // \}   
  
\#define MAXLINE 100  
char line\[MAXLINE\];  
int li= 0;  
int getline\_( char line\[\], int lim)\{  
     int i,c;  
    i= 0;  
     while(i<lim- 1&&((c=getchar())!=EOF)&&c!= ' \\n ')  
        line\[i++\]=c;  
     if(c==EOF&&i== 0)  
         return - 1;  
     if(c== ' \\n ')  
        line\[i++\]=c;  
    line\[i\]= ' \\0 ';  
     return i;  
\}  
\#define MAXOP 1000  
\#define NUMBER '0'  
int getop( char s\[\])\{  
     int i,c;  
     if(line\[li\]== ' \\0 ')  
         if(getline\_(line,MAXLINE)==- 1)  
             return EOF;  
         else  
            li= 0;  
     while((s\[ 0\]=c=line\[li++\])== '   '||c== ' \\t ')  
        ;  
    s\[ 1\]= ' \\0 ';  
     if(!isdigit(c)&&c!= ' . '&&c!= ' \- ')  
         return c;  
    i= 0;  
     if(c== ' \- ')  
         if(isdigit(c=line\[li++\])||c== ' . ')  
            s\[++i\]=c;  
         else  
        \{  
             if(c!=EOF)  
                li--;  
             return  ' \- ';  
        \}  
     if(isdigit(c))  
         while(isdigit(s\[++i\]=c=line\[li++\]))  
            ;  
     if(c== ' . ')  
         while(isdigit(s\[++i\]=c=line\[li++\]))  
            ;  
    s\[i\]= ' \\0 ';  
    li--;  
     return NUMBER;  
\}  
  
int main()\{  
     int type;  
     double op2;  
     char s\[MAXOP\];  
     while((type=getop(s))!=EOF)\{  
         switch(type)\{  
             case NUMBER:  
                push(atof\_(s));  
                 break;  
             case  ' \+ ':  
                push(pop()+pop());  
                 break;  
             case  ' \- ':  
                op2=pop();  
                push(pop()-op2);  
                 break;  
             case  ' \* ':  
                push(pop()\*pop());  
                 break;  
             case  ' / ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(pop()/op2);  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
             case  ' % ':  
                op2=pop();  
                 if(ABS(op2)>1e- 10)  
                    push(fmod(pop(),op2));  
                 else  
                    printf( " error:zero divisor\\n ");  
                 break;  
  
             case  ' \\n ':  
                printf( " \\t%.8g\\n ",pop());  
                 break;  
             default:  
                printf( " error: unknown command %s\\n ",s);  
                 break;  
        \}  
    \}  
\}

![复制代码][copycode.gif]

![201208051119532841.png][]

快速排序

![201208051119539776.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
// \#include <stdlib.h>   
 void swap( int \*x, int \*y)\{  
     int temp=\*x;  
    \*x=\*y;  
    \*y=temp;  
\}  
void qsort( int v\[\], int left, int right)\{  
     int i,last;  
     if(left>=right)  
         return;  
    swap(v+left,v+(left+right)/ 2);  
    last=left;  
     for(i=left+ 1;i<=right;i++)  
         if(v\[i\]<v\[left\]) \{  
            last++;  
            swap(v+last,v+i);  
        \}  
    swap(v+left,v+last);  
    qsort(v,left,last- 1);  
    qsort(v,last+ 1,right);  
\}  
void Qsort( int v\[\], int n)\{  
    qsort(v, 0,n- 1);  
\}  
  
void print\_arr( int v\[\], int n)\{  
     int i;  
     for(i= 0;i<n;i++)  
        printf( " %4d ",v\[i\]);  
    printf( " \\n ");  
\}  
int main()\{  
     int i;  
     for(i= 0;i< 10;i++)\{  
         int arr\[ 20\],j,b\[ 20\];  
         for(j= 0;j< 20;j++)  
        \{  
             int val=rand()% 1000;  
            arr\[j\]=val;  
            b\[j\]=val;  
        \}  
        printf( " before: ");  
        print\_arr(b, 20);  
        Qsort(arr, 20);  
        printf( " after : ");  
        print\_arr(arr, 20);  
    \}  
\}

![复制代码][copycode.gif]

测试结果如下：

![201208051119541379.png][]

swap宏

![201208051119549395.png][]

第5章 指针与数组

![20120805111954790.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

int strend( char \*s, char\*t)\{  
     char \*bs=s;  
     char \*bt=t;  
     while(\*s++);  
     while(\*t++);  
     while(\*--s==\*--t)\{  
         if(t==bt||s==st)  
             break;  
    \}  
     if(\*s==\*t&&t==bt&&\*s!= ' \\0 ')  
         return  1;  
     else                                
         return  0;  
\}

![复制代码][copycode.gif]

![201208051119541837.png][]  
![201208051119556264.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

void strncpy( char\* s, char \*t, int n)\{  
     while(\*t&&n--> 0)  
        \*s++=\*t++;  
     while(n--> 0)  
        \*s++= ' \\0 ';  
\}  
void strncat( char \*s, char \*t, int n)\{  
    strncpy(s+strlen(s),t,n);  
\}  
int strncmp( char\* s, char\* t, int n)\{  
     for(;\*s==\*t;s++,t++)  
         if(\*s== ' \\0 '||--n<= 0)  
             return  0;  
     return \*s-\*t;  
\}

![复制代码][copycode.gif]

UNIX系统中sort程序的一个简单版本，实现对输入文本的排序。

![201208051119552643.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include < string.h>  
\#include <stdlib.h>  
\#define MAXLINES 5000  
char \*lineptr\[MAXLINES\];  
  
\#define MAXLEN 1000  
  
int getline\_( char line\[\], int lim)\{  
     int i,c;  
    i= 0;  
     while(i<lim- 1&&((c=getchar())!=EOF)&&c!= ' \\n ')  
        line\[i++\]=c;  
     if(c==EOF&&i== 0)  
         return - 1;  
     if(c== ' \\n ')  
        line\[i++\]=c;  
    line\[i\]= ' \\0 ';  
     return i;  
\}  
char\* alloc( int len)\{  
     char \*p=( char\*)malloc(len\* sizeof( char));  
     return p;  
\}  
int readlines( char\* lineptr\[\], int maxlines)\{  
     int len,nlines;  
     char \*p,line\[MAXLEN\];  
    nlines= 0;  
     while((len=getline\_(line,MAXLEN))> 0)  
         if(nlines>=maxlines||(p=alloc(len))==NULL)  
             return - 1;  
     else\{  
        line\[len- 1\]= ' \\0 ';  
        strcpy(p,line);  
        lineptr\[nlines++\]=p;  
    \}  
     return nlines;  
\}  
void writelines( char \*lineptr\[\], int nlines)\{  
     int i;  
     for(i= 0;i<nlines;i++)  
        printf( " %s\\n ",lineptr\[i\]);  
\}  
void swap( char \*\*x, char \*\*y)\{  
     char\*tmp;  
    tmp=\*x;  
    \*x=\*y;  
    \*y=tmp;  
\}  
void qsort\_( char \*v\[\], int left, int right)\{  
     int i,last;  
     if(left>=right)  
         return ;  
    swap(v+left,v+(left+right)/ 2);  
    last=left;  
     for(i=left+ 1;i<=right;i++)  
         if(strcmp(v\[i\],v\[left\])< 0)  
        \{  
            last++;  
            swap(v+last,v+i);  
        \}  
    swap(v+left,v+last);  
    qsort\_(v,left,last- 1);  
    qsort\_(v,last+ 1,right);  
\}  
int main()\{  
     int nlines;  
     int i;  
     if((nlines=readlines(lineptr,MAXLINES))> 0)\{  
        qsort\_(lineptr, 0,nlines- 1);  
        writelines(lineptr,nlines);  
         for(i= 0;i<nlines;i++)  
            free(lineptr\[i\]);  
  
         return  0;  
    \}  
     else\{  
        printf( " error: input too big to sort\\n ");  
         return  1;  
    \}  
\}

![复制代码][copycode.gif]

根据日期计算是一年的第几天：

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

static  int daytab\[\]\[ 13\]=\{ \{ 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31\}  
,\{ 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31\}\};  
int day\_of\_year( int year, int month, int day)\{  
     int i,leap;  
    leap=year% 4== 0&&year% 100!= 0||year% 400== 0;  
     if(month< 1||month> 12)  
         return - 1;  
     if(day< 1||day>daytab\[leap\]\[month\])  
         return - 1;  
     for(i= 1;i<month;i++)  
        day+=daytab\[leap\]\[i\];  
     return day;  
\}  
void month\_day( int year, int yearday, int \*pmonth, int \*pday)\{  
     int i,leap;  
     if(year< 1)\{  
        \*pmonth=- 1;  
        \*pday=- 1;  
         return ;  
    \}  
    leap=year% 4== 0&&year% 100!= 0||year% 400== 0;  
     for(i= 1;i<= 12&&yearday>daytab\[leap\]\[i\];i++)  
        yearday-=daytab\[leap\]\[i\];  
     if(i> 12&&yearday>daytab\[leap\]\[ 12\])\{                           
        \*pmonth=- 1;  
        \*pday=- 1;  
    \}  
     else\{  
        \*pmonth=i;  
        \*pday=yearday;  
    \}  
\}

![复制代码][copycode.gif]

习题5-13

![201208051119556754.png][]

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\#include <stdio.h>  
\#include <stdlib.h>  
\#include < string.h>  
\#define DEFLINES 10  
\#define MAXLINES 10  
\#define MAXLEN 100  
int getline\_( char line\[\], int lim)\{  
     int i,c;  
    i= 0;  
     while(i<lim- 1&&((c=getchar())!=EOF)&&c!= ' \\n ')  
        line\[i++\]=c;  
     if(c==EOF&&i== 0)  
         return - 1;  
     if(c== ' \\n ')  
        line\[i++\]=c;  
    line\[i\]= ' \\0 ';  
     return i;  
\}  
void error( char \*s)\{  
    printf( " %s\\n ",s);  
    exit( 1);  
\}  
int main( int argc, char\* argv\[\])\{  
     char \*p,\*buf,\*bufend;  
     char line\[MAXLEN\];  
     char \*lineptr\[MAXLINES\];  
     int first,i,last,len,n,nlines;  
     if(argc== 1)  
        n=DEFLINES;  
     else  if(argc== 2&&(\*++argv)\[ 0\]== ' \- ')  
        n=atoi(argv\[ 0\]+ 1);  
     if(n< 1||n>MAXLINES)  
        n=MAXLINES;  
     for(i= 0;i<MAXLINES;i++)  
        lineptr\[i\]=NULL;  
     if((p=buf=malloc(MAXLINES\*MAXLEN))==NULL)  
        error( " tail:cannot allocate buf ");  
    bufend=buf+MAXLINES\*MAXLEN;  
    last= 0;  
    nlines= 0;  
     while((len=getline\_(line,MAXLEN))> 0)\{  
         if(p+len+ 1>=bufend)  
            p=buf;  
        lineptr\[last\]=p;  
        strcpy(lineptr\[last\],line);  
         if(++last>=MAXLINES)  
            last= 0;  
        p+=len+ 1;  
        nlines++;  
    \}  
     if(n>nlines)  
        n=nlines;  
    first=last-n;  
     if(first< 0)  
        first+=MAXLINES;  
     for(i=first;n--> 0;i=(i+ 1)%MAXLINES)  
        printf( " %s ",lineptr\[i\]);  
    free(buf);  
  
     return  0;  
\}

![复制代码][copycode.gif]

![201208051119568117.png][]

![201208051119564180.png][]

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\#include <stdio.h>  
\#include < string.h>  
\#include <stdlib.h>  
\#include <ctype.h>  
  
\#define NUMERIC 1  
\#define DECR 2  
\#define FOLD 4  
\#define DIR 8  
// \#define LINES 100   
 \#define MAXLINES 100  
  
\#define MAXLEN 1000  
char option= 0;  
int pos1= 0;  
int pos2= 0;  
  
int getline\_( char line\[\], int lim)\{  
     int i,c;  
    i= 0;  
     while(i<lim- 1&&((c=getchar())!=EOF)&&c!= ' \\n ')  
        line\[i++\]=c;  
     if(c==EOF&&i== 0)  
         return - 1;  
     if(c== ' \\n ')  
        line\[i++\]=c;  
    line\[i\]= ' \\0 ';  
     return i;  
\}  
void error( char \*s)\{  
    printf( " %s\\n ",s);  
    exit( 1);  
\}  
char\* alloc( int len)\{  
     char \*p=( char\*)malloc(len\* sizeof( char));  
     return p;  
\}  
int readlines( char\* lineptr\[\], int maxlines)\{  
     int len,nlines;  
     char \*p,line\[MAXLEN\];  
    nlines= 0;  
     while((len=getline\_(line,MAXLEN))> 0)  
         if(nlines>=maxlines||(p=alloc(len))==NULL)  
             return - 1;  
     else\{  
        line\[len- 1\]= ' \\0 ';  
        strcpy(p,line);  
        lineptr\[nlines++\]=p;  
    \}  
     return nlines;  
\}  
void writelines( char \*lineptr\[\], int nlines, int decr)\{  
     int i;  
     if(decr)  
         for(i=nlines- 1;i>= 0;i--)  
            printf( " %s\\n ",lineptr\[i\]);  
     else  
         for(i= 0;i<nlines;i++)  
            printf( " %s\\n ",lineptr\[i\]);  
\}  
void swap( void\*\*x, void\*\*y)\{  
     void\*tmp;  
    tmp=\*x;  
    \*x=\*y;  
    \*y=tmp;  
\}  
void qsort\_( void\*v\[\], int left, int right,  
         int(\*comp)( void\*, void\*))\{  
     int i,last;  
     if(left>=right)  
         return ;  
    swap(v+left,v+(left+right)/ 2);  
    last=left;  
     for(i=left+ 1;i<=right;i++)  
         if(strcmp(v\[i\],v\[left\])< 0)  
        \{  
            last++;  
            swap(v+last,v+i);  
        \}  
    swap(v+left,v+last);  
    qsort\_(v,left,last- 1,comp);  
    qsort\_(v,last+ 1,right,comp);  
\}  
void readargs( int argc, char\*argv\[\])\{  
     int c;  
     while(--argc> 0&&(c=(\*++argv)\[ 0\])== ' \- '||c== ' \+ ')\{  
         if(c== ' \- '&&!isdigit(\*(argv\[ 0\]+ 1)))  
             while(c=\*++argv\[ 0\])  
                 switch(c)\{  
                     case  ' d ':  
                        option|=DIR;  
                         break;  
                     case  ' f ':  
                        option|=FOLD;  
                         break;  
                     case  ' n ':  
                        option|=NUMERIC;  
                         break;  
                     case  ' r ':  
                        option|=DECR;  
                         break;  
                     default:  
                        printf( " sort: illegal option %c\\n ",c);  
                        error( " usage: sort -dfnr \[+pos1\] \[-pos2\] ");  
                         break;  
                \}  
         else  if(c== ' \- ')  
            pos2=atoi(argv\[ 0\]+ 1);  
         else  if((pos1=atoi(argv\[ 0\]+ 1))< 0)  
            error( " usage: sort -dfnr \[+pos1\] \[-pos2\] ");  
    \}  
     if(argc||pos1>pos2)  
            error( " usage: sort -dfnr \[+pos1\] \[-pos2\] ");  
\}  
\#define MAXSTR 100  
void substr( char \*s, char \*str)\{  
     int i,j,len;  
    len=strlen(s);  
     if(pos2> 0&&len>pos2)  
        len=pos2;  
     else  if(pos2> 0&&len<pos2)  
        error( " substr:string too short ");  
     for(j= 0,i=pos1;i<len;i++,j++)  
        str\[j\]=s\[i\];  
    str\[j\]= ' \\0 ';  
\}  
\#define ABS(x) ((x)<0?-(x):(x))  
  
double atof\_( char s\[\])\{  
     double val,power;  
     int i,sign;  
     for(i= 0;isspace(s\[i\]);i++);  
    sign=(s\[i\]== ' \- ')?- 1: 1;  
     if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
        i++;  
     for(val= 0.0;isdigit(s\[i\]);i++)  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
     if(s\[i\]== ' . ')  
        i++;  
     for(power= 1.0;isdigit(s\[i\]);i++)\{  
        val= 10.0\*val+(s\[i\]- ' 0 ');  
        power\*= 10;  
    \}  
    val= sign\*val/power;  
     if(s\[i\]== ' e '||s\[i\]== ' E ')\{  
         int exp;  
        sign=(s\[++i\]== ' \- ')?- 1: 1;  
         if(s\[i\]== ' \+ '||s\[i\]== ' \- ')  
            i++;  
         for(exp= 0;isdigit(s\[i\]);i++)  
            exp= 10\*exp+(s\[i\]- ' 0 ');  
         if(sign)  
             while(exp--> 0)  
                val\*= 10;  
         else  
             while(exp--> 0)  
                val/= 10;  
    \}  
     return val;  
\}  
int numcmp( char \*s1, char \*s2)\{  
     double v1,v2;  
     char str\[MAXSTR\];  
    substr(s1,str);  
    v1=atof\_(str);  
    substr(s2,str);  
    v2=atof\_(str);  
     if(v1<v2)  
         return - 1;  
     else  if(v1>v2)  
         return  1;  
     else   
         return  0;  
\}  
// \#define FOLD 4  
 // \#define DIR 8   
 int charcmp( char \*s, char \*t)\{  
     char a,b;  
     int i,j,endpos;  
     int fold=(option&FOLD)? 1: 0;  
     int dir=(option&DIR)? 1: 0;  
    i=j=pos1;  
     if(pos2> 0)  
        endpos=pos2;  
     else  if((endpos-strlen(s))>strlen(t))  
        endpos=strlen(t);  
     do\{  
         if(dir)\{  
             while(i<endpos&&!isalnum(s\[i\])&&  
                    s\[i\]!= '   '&&s\[i\]!= ' \\0 ')  
                i++;  
             while(j<endpos&&!isalnum(t\[j\])&&  
                    t\[j\]!= '   '&&t\[j\]!= ' \\0 ')  
                j++;  
        \}  
         if(i<endpos&&j<endpos)\{  
            a=fold?tolower(s\[i\]):s\[i\];  
            i++;  
            b=fold?tolower(t\[j\]):t\[j\];  
            j++;  
             if(a==b&&a== ' \\0 ')  
                 return  0;  
        \}  
    \}  
     while(a==b&&i<endpos&&j<endpos);  
     return a-b;  
\}  
int main( int argc, char\*argv\[\])\{  
     char \*lineptr\[MAXLINES\];  
     int nlines;  
     int i;  
    readargs(argc,argv);  
     if((nlines=readlines(lineptr,MAXLINES))> 0)\{  
         if(option&NUMERIC)  
            qsort\_(( void\*\*)lineptr, 0,nlines- 1,  
                    ( int(\*)( void\*, void\*))numcmp);  
         else  
            qsort\_(( void\*\*)lineptr, 0,nlines- 1,  
                    ( int(\*)( void\*, void\*))charcmp);  
        writelines(lineptr,nlines,option&DECR);  
         for(i= 0;i<nlines;i++)  
            free(lineptr\[i\]);  
  
         return  0;  
    \}  
     else\{  
        printf( " error: input too big to sort\\n ");  
         return  1;  
    \}  
\}

![复制代码][copycode.gif]

![201208051119568051.png][]

dcl一个比较不错的程序：将声明转化为文字描述或将文字描述转化为声明

![201208051119571921.png][]

![201208051119577985.png][]

![201208051119579031.png][]

![201208051119585967.png][]

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![复制代码][copycode.gif]

\#include <stdio.h>  
\#include < string.h>  
\#include <ctype.h>  
\#define MAXTOKEN 100  
  
enum\{NAME,PARENS,BRACKETS\};  
  
int tokentype;  
char token\[MAXTOKEN\];  
char name\[MAXTOKEN\];  
char datatype\[MAXTOKEN\];  
char  out\[ 1000\];  
  
\#define BUFSIZE 10  
char buf\[BUFSIZE\];  
int bufp= 0;  
int getch( void)\{  
     return bufp> 0?buf\[--bufp\]:getchar();  
\}  
void ungetch( int c)\{  
     if(bufp>=BUFSIZE)  
        printf( " ungetch: too many characters\\n ");  
     else  
        buf\[bufp++\]=c;  
\}  
  
int gettoken()\{  
     char \*p=token;  
     int c;  
     while((c=getch())== '   '||c== ' \\t ')  
        ;  
     if(c== ' ( ')\{  
         if((c=getch())== ' ) ')\{  
            strcpy(token, " () ");  
             return tokentype=PARENS;  
        \}  
         else\{  
            ungetch(c);  
             return tokentype= ' ( ';  
        \}  
    \}  
     else  if(c== ' \[ ')\{  
         for(\*p++=c;(\*p++=getch())!= ' \] ';)  
            ;  
        \*p= ' \\0 ';  
         return tokentype=BRACKETS;  
    \}  
     else  if(isalpha(c))\{  
         for(\*p++=c;isalnum(c=getch());)  
            \*p++=c;  
        \*p= ' \\0 ';  
        ungetch(c);  
         return tokentype=NAME;  
    \}  
     else  
         return tokentype=c;  
\}  
  
void dcl( void);  
void dirdcl( void)\{  
     int type;  
     if(tokentype== ' ( ')\{  
        dcl();  
         if(tokentype!= ' ) ')  
            printf( " error:missing )\\n ");  
    \}  
     else  if(tokentype==NAME)  
        strcpy(name,token);  
     else  
        printf( " error:expected name or (dcl)\\n ");  
     while((type=gettoken())==PARENS||type==BRACKETS)  
         if(type==PARENS)  
            strcat( out, "  function returning ");  
     else\{  
        strcat( out,  "  array ");  
        strcat( out,token);  
        strcat( out, "  of ");  
    \}  
\}  
void dcl( void)\{  
     int ns;  
     for(ns= 0;gettoken()== ' \* ';)  
        ns++;  
    dirdcl();  
     while(ns--> 0)  
        strcat( out, "  pointer to ");  
\}  
  
int main()\{  
     while(gettoken()!=EOF)\{  
        strcpy(datatype,token);  
         out\[ 0\]= ' \\0 ';  
        dcl();  
         if(tokentype!= ' \\n ')  
            printf( " syntax error\\n ");  
        printf( " %s: %s %s\\n ",name, out,datatype);  
    \}  
     return  0;  
\}

![复制代码][copycode.gif]

![201208051119581822.png][]

![201208051119581474.png][]

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int main()\{  
     int type;  
     char temp\[MAXTOKEN\];  
     while(gettoken()!=EOF)\{  
        strcpy( out,token);  
         while((type=gettoken())!= ' \\n ')  
             if(type==PARENS||type==BRACKETS)  
                strcat( out,token);  
         else  if(type== ' \* ')\{  
            sprintf(temp, " (\*%s) ", out);  
            strcpy( out,temp);  
        \}  
         else  if(type==NAME)\{  
            sprintf(temp, " %s %s ",token, out);  
            strcpy( out,temp);  
        \}  
         else \{  
            printf( " invalid input at %s\\n ",token);  
        \}  
    \}  
  
    printf( " %s\\n ", out);                               
     return  0;  
\}

![复制代码][copycode.gif]

![201208051119587329.png][]

![20120805111958361.png][]

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int nexttoken()\{  
     int type;  
    type=gettoken();  
    prevtoken=YES;  
     return type;  
\}  
int main()\{  
     int type;  
     char temp\[MAXTOKEN\];  
     while(gettoken()!=EOF)\{  
        strcpy( out,token);  
         while((type=gettoken())!= ' \\n ')  
             if(type==PARENS||type==BRACKETS)  
                strcat( out,token);  
         else  if(type== ' \* ')\{  
             if((type=nexttoken())==PARENS||               
                    type==BRACKETS)  
            sprintf(temp, " (\*%s) ", out);  
             else  
                sprintf(temp, " \*%s ", out);  
            strcpy( out,temp);  
        \}  
         else  if(type==NAME)\{  
            sprintf(temp, " %s %s ",token, out);  
            strcpy( out,temp);  
        \}  
         else \{  
            printf( " invalid input at %s\\n ",token);  
        \}  
    \}  
  
    printf( " %s\\n ", out);  
     return  0;  
\}

![复制代码][copycode.gif]

![201208051119597197.png][]

![201208051120002147.png][]

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\#include <stdio.h>  
\#include < string.h>  
\#include <ctype.h>  
\#define MAXTOKEN 100  
  
enum\{NAME,PARENS,BRACKETS\};  
enum\{NO,YES\};  
  
int tokentype;  
char token\[MAXTOKEN\];  
char name\[MAXTOKEN\];  
char datatype\[MAXTOKEN\];  
char  out\[ 1000\];  
int prevtoken=NO;  
  
\#define BUFSIZE 10  
char buf\[BUFSIZE\];  
int bufp= 0;  
int getch( void)\{  
     return bufp> 0?buf\[--bufp\]:getchar();  
\}  
void ungetch( int c)\{  
     if(bufp>=BUFSIZE)  
        printf( " ungetch: too many characters\\n ");  
     else  
        buf\[bufp++\]=c;  
\}  
void errmsg( char \*msg)\{  
    printf( " %s ",msg);  
    prevtoken=YES;  
\}  
  
int gettoken()\{  
     char \*p=token;  
     int c;  
     if(prevtoken==YES)\{  
        prevtoken=NO;  
         return tokentype;  
    \}  
     while((c=getch())== '   '||c== ' \\t ')  
        ;  
     if(c== ' ( ')\{  
         if((c=getch())== ' ) ')\{  
            strcpy(token, " () ");  
             return tokentype=PARENS;  
        \}  
         else\{  
            ungetch(c);  
             return tokentype= ' ( ';  
        \}  
    \}  
     else  if(c== ' \[ ')\{  
         for(\*p++=c;(\*p++=getch())!= ' \] ';)  
            ;  
        \*p= ' \\0 ';  
         return tokentype=BRACKETS;  
    \}  
     else  if(isalpha(c))\{  
         for(\*p++=c;isalnum(c=getch());)  
            \*p++=c;  
        \*p= ' \\0 ';  
        ungetch(c);  
         return tokentype=NAME;  
    \}  
     else  
         return tokentype=c;  
\}  
  
int compare( char \*\*s, char \*\*t)\{  
     return strcmp(\*s,\*t);  
\}  
  
int typespec( void)\{  
     static  char \*types\[\]=\{  
         " char ", " int ", " void "  
    \};  
     char \*pt=token;  
     if(bsearch(&pt,types, sizeof(types)/ sizeof( char\*), sizeof( char\*),compare)==NULL)  
         return NO;  
     else  
         return YES;  
\}  
int typequal( void)\{  
     static  char \*typeq\[\]=\{  
         " const ", " volatile "  
    \};  
     char \*pt=token;  
     if(bsearch(&pt,typeq, sizeof(typeq)/ sizeof( char\*), sizeof( char\*),compare)==NULL)  
         return NO;  
     else  
         return YES;  
\}  
void dcl( void);  
void dclspec( void)\{  
     char temp\[MAXTOKEN\];  
    temp\[ 0\]= ' \\0 ';  
    gettoken();  
     do\{  
         if(tokentype!=NAME)\{  
            prevtoken=YES;  
            dcl();  
        \}  
         else  if(typespec()==YES)\{  
            strcat(temp, "   ");  
            strcat(temp,token);  
            gettoken();  
        \}  
         else  if(typequal()==YES)\{  
            strcat(temp, "   ");  
            strcat(temp,token);  
            gettoken();  
        \}  
         else  
            errmsg( " unknown type in parameter list\\n ");  
    \}  
     while(tokentype!= ' , '&&tokentype!= ' ) ');  
    strcat( out,temp);  
     if(tokentype== ' , ')  
        strcat( out, " , ");  
\}  
void parmdcl( void)\{  
     do\{  
        dclspec();  
    \} while(tokentype== ' , ');  
     if(tokentype!= ' ) ')  
        errmsg( " missing ) in parameter declaration\\n ");  
\}  
void dirdcl( void)\{  
     int type;  
     if(tokentype== ' ( ')\{  
        dcl();  
         if(tokentype!= ' ) ')  
            printf( " error:missing )\\n ");  
    \}  
     else  if(tokentype==NAME) \{  
         if(name\[ 0\]== ' \\0 ')  
            strcpy(name,token);  
    \}  
     else  
        prevtoken=YES;  
     while((type=gettoken())==PARENS||type==BRACKETS||type== ' ( ')  
         if(type==PARENS)  
            strcat( out, "  function returning ");  
     else  if(type== ' ( ')\{  
        strcat( out, "  function expecting ");  
        parmdcl();  
        strcat( out, "  and returning ");  
    \}  
         else\{  
        strcat( out,  "  array ");  
        strcat( out,token);  
        strcat( out, "  of ");  
    \}  
\}  
void dcl( void)\{  
     int ns;  
     for(ns= 0;gettoken()== ' \* ';)  
        ns++;  
    dirdcl();  
     while(ns--> 0)  
        strcat( out, "  pointer to ");  
\}  
  
int main()\{  
     while(gettoken()!=EOF)\{  
        strcpy(datatype,token);  
         out\[ 0\]= ' \\0 ';  
        dcl();  
         if(tokentype!= ' \\n ')  
            printf( " syntax error\\n ");  
        printf( " %s: %s %s\\n ",name, out,datatype);  
    \}  
     return  0;  
\}

![复制代码][copycode.gif]

![201208051120019540.png][]

这个网站很不错的：[http://cdecl.org/][http_cdecl.org]

第6章 结构体

统计关键字出现的次数

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\#include <stdio.h>  
\#include <stdlib.h>  
\#include <ctype.h>  
\#include < string.h>  
  
\#define MAXWORD 1000  
struct key \{  
     char \*word;  
     int count;  
\}  
keytab\[\]=\{  
     " auto ", 0,  
     " break ", 0,  
     " case ", 0,  
     " char ", 0,  
     " const ", 0,  
     " continue ", 0,  
     " default ", 0,  
     " do ", 0,  
     " double ", 0,  
     " else ", 0,  
     " enum ", 0,  
     " extern ", 0,  
     " float ", 0,  
     " for ", 0,  
     " goto ", 0,  
     " if ", 0,  
     " int ", 0,  
     " long ", 0,  
     " register ", 0,  
     " return ", 0,  
     " short ", 0,  
     " signed ", 0,  
     " sizeof ", 0,  
     " static ", 0,  
     " struct ", 0,  
     " switch ", 0,  
     " typedef ", 0,  
     " union ", 0,  
     " unsigned ", 0,  
     " void ", 0,  
     " volatile ", 0,  
     " while ", 0,  
\};  
\#define NKEYS (sizeof keytab/sizeof(keytab\[0\]))  
\#define BUFSIZE 10                                   
char buf\[BUFSIZE\];                                   
int bufp= 0;                                          
int getch( void)\{                                     
     return bufp> 0?buf\[--bufp\]:getchar();             
\}                                                    
void ungetch( int c)\{                                 
     if(bufp>=BUFSIZE)                                
        printf( " ungetch: too many characters\\n ");    
     else                                             
        buf\[bufp++\]=c;                               
\}                                                    
int binsearch( char \*word, struct key tab\[\], int n)\{  
     int cond;  
     int low,high,mid;  
    low= 0;  
    high=n- 1;  
     while(low<=high)\{  
        mid=(low+high)/ 2;  
         if((cond=strcmp(word,tab\[mid\].word))< 0)  
            high=mid- 1;  
         else  if(cond> 0)  
            low=mid+ 1;  
         else  
             return mid;  
    \}  
     return - 1;  
\}  
int comment( void)\{  
     int c;  
     while((c=getch())!=EOF)  
         if(c== ' \* ')  
             if((c=getch())== ' / ')  
                 break;  
             else  
                ungetch(c);  
     return c;  
\}  
int getword( char \*word, int lim)\{  
     char \*w=word;  
     int c,d;  
     while(isspace(c=getch()))  
        ;  
     if(c!=EOF)  
        \*w++=c;  
     if(isalpha(c)||c== ' \- '||c== ' \# ')\{  
         for(;--lim> 0;w++)  
             if(!isalnum(\*w=getch())&&\*w!= ' \- ')\{  
                ungetch(\*w);  
                 break;  
            \}  
    \}  
     else  if(c== ' \\' '||c== ' " ')\{  
         for(;--lim> 0;w++)  
             if((\*w=getch())== ' \\\\ ')  
                \*++w=getch();  
         else  if(\*w==c)\{  
            w++;  
             break;  
        \}  
         else  if(\*w==EOF)  
             break;  
              
    \}  
     else  if(c== ' / ')  
         if((d=getch())== ' \* ')  
            c=comment();  
     else  
        ungetch(d);  
    \*w= ' \\0 ';  
     return c;  
\}  
int main()\{  
     int n;  
     char word\[MAXWORD\];  
     while(getword(word,MAXWORD)!=EOF)  
         if(isalpha(word\[ 0\]))  
             if((n=binsearch(word,keytab,NKEYS))>= 0)  
                keytab\[n\].count++;  
     for(n= 0;n<NKEYS;n++)  
         if(keytab\[n\].count> 0)  
            printf( " %4d %s\\n ",  
                    keytab\[n\].count,keytab\[n\].word);  
     return  0;  
\}

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\#include <stdio.h>  
\#include <ctype.h>  
\#include < string.h>  
\#include <stdlib.h>  
\#define BUFSIZE 10                                   
char buf\[BUFSIZE\];                                   
int bufp= 0;                                          
int getch( void)\{                                     
     return bufp> 0?buf\[--bufp\]:getchar();             
\}                                                    
void ungetch( int c)\{                                 
     if(bufp>=BUFSIZE)                                
        printf( " ungetch: too many characters\\n ");    
     else                                             
        buf\[bufp++\]=c;                               
\}                                                    
int comment( void)\{  
     int c;  
     while((c=getch())!=EOF)  
         if(c== ' \* ')  
             if((c=getch())== ' / ')  
                 break;  
             else  
                ungetch(c);  
     return c;  
\}  
int getword( char \*word, int lim)\{  
     char \*w=word;  
     int c,d;  
     while(isspace(c=getch()))  
        ;  
     if(c!=EOF)  
        \*w++=c;  
     if(isalpha(c)||c== ' \- '||c== ' \# ')\{  
         for(;--lim> 0;w++)  
             if(!isalnum(\*w=getch())&&\*w!= ' \- ')\{  
                ungetch(\*w);  
                 break;  
            \}  
    \}  
     else  if(c== ' \\' '||c== ' " ')\{  
         for(;--lim> 0;w++)  
             if((\*w=getch())== ' \\\\ ')  
                \*++w=getch();  
         else  if(\*w==c)\{  
            w++;  
             break;  
        \}  
         else  if(\*w==EOF)  
             break;  
              
    \}  
     else  if(c== ' / ')  
         if((d=getch())== ' \* ')  
            c=comment();  
     else  
        ungetch(d);  
    \*w= ' \\0 ';  
     return c;  
\}  
struct tnode\{  
     char \*word;  
     int match;  
     struct tnode \*left;  
     struct tnode \*right;  
\};  
\#define MAXWORD 100  
\#define YES 1  
\#define NO 0  
  
int compare( char \*s, struct tnode \*p, int num, int \*found)\{  
     int i;  
     char \*t=p->word;  
     for(i= 0;\*s==\*t;i++,s++,t++)  
         if(\*s== ' \\0 ')  
             return  0;  
     if(i>=num)\{  
        \*found=YES;  
        p->match=YES;  
    \}  
     return \*s-\*t;  
\}  
struct tnode\* talloc( void)\{  
     return ( struct tnode\*)malloc( sizeof( struct tnode));  
\}  
char \*strdup\_( char \*s)\{  
     char \*p;  
    p=( char\*)malloc(strlen(s)+ 1);  
     if(p!=NULL)  
        strcpy(p,s);  
     return p;  
\}  
  
struct tnode\* addtreex( struct tnode\*p, char \*w, int num, int \*found)\{  
     int cond;  
     if(p==NULL)\{  
        p=talloc();  
        p->word=strdup\_(w);  
        p->match=\*found;  
        p->left=p->right=NULL;  
    \}  
     else  if((cond=compare(w,p,num,found))< 0)  
        p->left=addtreex(p->left,w,num,found);  
     else  if(cond> 0)  
        p->right=addtreex(p->right,w,num,found);  
     return p;  
\}  
void treeprint( struct tnode\* p)\{  
     if(p!=NULL)\{  
        treeprint(p->left);  
         if(p->match)  
            printf( " %s\]n ",p->word);  
        treeprint(p->right);  
    \}  
\}  
void freetree( struct tnode\*p)\{  
     if(p!=NULL)\{  
        freetree(p->left);  
        freetree(p->right);  
        free(p->word);  
    \}  
\}  
  
int main( int argc, char \*argv\[\])\{  
     struct tnode \*root;  
     char word\[MAXWORD\];  
     int found=NO;  
     int num;  
    num=(--argc&&(\*++argv)\[ 0\]== ' \- ')?atoi(argv\[ 0\]+ 1): 6;  
    root=NULL;  
     while(getword(word,MAXWORD)!=EOF)\{  
         if(isalpha(word\[ 0\])&&strlen(word)>=num)  
            root=addtreex(root,word,num,&found);  
        found=NO;  
    \}  
    treeprint(root);  
    freetree(root);  
     return  0;  
\}

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\#include <stdio.h>  
\#include <ctype.h>  
\#include < string.h>  
\#include <stdlib.h>  
\#define BUFSIZE 10                                   
char buf\[BUFSIZE\];                                   
int bufp= 0;                                          
int getch( void)\{                                     
     return bufp> 0?buf\[--bufp\]:getchar();             
\}                                                    
void ungetch( int c)\{                                 
     if(bufp>=BUFSIZE)                                
        printf( " ungetch: too many characters\\n ");    
     else                                             
        buf\[bufp++\]=c;                               
\}                                                    
int comment( void)\{  
     int c;  
     while((c=getch())!=EOF)  
         if(c== ' \* ')  
             if((c=getch())== ' / ')  
                 break;  
             else  
                ungetch(c);  
     return c;  
\}  
int getword( char \*word, int lim)\{  
     char \*w=word;  
     int c,d;  
     while(isspace(c=getch()))  
        ;  
     if(c!=EOF)  
        \*w++=c;  
     if(isalpha(c)||c== ' \- '||c== ' \# ')\{  
         for(;--lim> 0;w++)  
             if(!isalnum(\*w=getch())&&\*w!= ' \- ')\{  
                ungetch(\*w);  
                 break;  
            \}  
    \}  
     else  if(c== ' \\' '||c== ' " ')\{  
         for(;--lim> 0;w++)  
             if((\*w=getch())== ' \\\\ ')  
                \*++w=getch();  
         else  if(\*w==c)\{  
            w++;  
             break;  
        \}  
         else  if(\*w==EOF)  
             break;  
              
    \}  
     else  if(c== ' / ')  
         if((d=getch())== ' \* ')  
            c=comment();  
     else  
        ungetch(d);  
    \*w= ' \\0 ';  
     return c;  
\}  
struct linklist\{  
     int lnum;  
     struct linklist \*ptr;  
\};  
struct tnode\{  
     char \*word;  
     struct linklist \*lines;  
     struct tnode \*left;  
     struct tnode \*right;  
\};  
\#define MAXWORD 100  
\#define YES 1  
\#define NO 0  
  
struct tnode\* talloc( void)\{  
     return ( struct tnode\*)malloc( sizeof( struct tnode));  
\}  
struct linklist \*lalloc( void)\{  
     return ( struct linklist\*)malloc( sizeof( struct linklist));  
\}  
char \*strdup\_( char \*s)\{  
     char \*p;  
    p=( char\*)malloc(strlen(s)+ 1);  
     if(p!=NULL)  
        strcpy(p,s);  
     return p;  
\}  
void addln( struct tnode \*p, int linenum)\{  
     struct linklist \*temp;  
    temp=p->lines;  
     while(temp->ptr!=NULL&&temp->lnum!=linenum)  
        temp=temp->ptr;  
     if(temp->lnum==linenum)\{  
        temp->ptr=lalloc();  
        temp->ptr->lnum=linenum;  
        temp->ptr->ptr=NULL;  
    \}  
\}  
  
struct tnode\* addtreex( struct tnode\*p, char \*w, int linenum)\{  
     int cond;  
     if(p==NULL)\{  
        p=talloc();  
        p->word=strdup\_(w);  
        p->lines=lalloc();  
        p->lines->lnum=linenum;  
        p->lines->ptr=NULL;  
        p->left=p->right=NULL;  
    \}  
     else  if((cond=strcmp(w,p->word))< 0)  
        p->left=addtreex(p->left,w,linenum);  
     else  if(cond> 0)  
        p->right=addtreex(p->right,w,linenum);  
     else  
        addln(p,linenum);  
     return p;  
\}  
void treeprint( struct tnode\* p)\{  
     struct linklist \*temp;  
     if(p!=NULL)\{  
        treeprint(p->left);  
        printf( " %10s:  ",p->word);  
         for(temp=p->lines;temp!=NULL;temp=temp->ptr)  
            printf( " %4d  ",temp->lnum);  
        printf( " \\n ");  
        treeprint(p->right);  
    \}  
\}  
void freetree( struct tnode\*p)\{  
     if(p!=NULL)\{  
        freetree(p->left);  
        freetree(p->right);  
        free(p->word);  
        free(p->lines);  
    \}  
\}  
int noiseword( char \*w)\{  
     static  char \*nw\[\]=\{  
         " a ", " an ", " and ", " are ", " in ", " is ", " of ", " or ", " that ", " the ", " this ", " to "  
    \};  
     int cond,mid;  
     int low= 0;  
     int high= sizeof(nw)/ sizeof( char\*)- 1;  
     while(low<=high)\{  
        mid=(low+high)/ 2;  
         if((cond=strcmp(w,nw\[mid\]))< 0)  
            high=mid- 1;  
         else  if(cond> 0)  
            low=mid+ 1;  
         else   
             return mid;  
    \}  
     return - 1;  
\}  
  
int main( int argc, char \*argv\[\])\{  
     struct tnode \*root;  
     char word\[MAXWORD\];  
     int linenum= 1;  
    root=NULL;  
     while(getword(word,MAXWORD)!=EOF)\{  
         if(isalpha(word\[ 0\])&&noiseword(word)==- 1)  
            root=addtreex(root,word,linenum);  
         else  if(word\[ 0\]== ' \\n ')  
            linenum++;  
    \}  
    treeprint(root);  
    freetree(root);  
     return  0;  
\}

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表查找程序核心代码：

![201208051120033802.png][]

![201208051120032374.png][]

![20120805112003945.png][]

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\#include <stdio.h>  
\#include < string.h>  
\#include <stdlib.h>  
struct nlist\{  
     struct nlist \*next;  
     char \*name;  
     char \*defn;  
\};  
\#define HASHSIZE 101  
static  struct nlist \*hashtab\[HASHSIZE\];  
unsigned hash( char \*s)  
\{  
    unsigned hashval;  
     for(hashval= 0;\*s!= ' \\0 ';s++)  
        hashval=\*s+ 32\*hashval;  
     return hashval%HASHSIZE;  
\}  
struct nlist \*lookup( char \*s)\{  
     struct nlist \*np;  
     for(np=hashtab\[hash(s)\];np!=NULL;np=np->next)  
         if(strcmp(s,np->name)== 0)  
             return np;  
     return NULL;  
\}  
struct nlist \*install( char \*name, char\*defn)\{  
     struct nlist \*np;  
    unsigned hashval;  
     if((np=lookup(name))==NULL)\{  
        np=( struct nlist \*)malloc( sizeof( struct nlist));  
         if(np==NULL||(np->name=strdup(name))==NULL)  
             return NULL;  
        hashval=hash(name);  
        np->next=hashtab\[hashval\];  
        hashtab\[hashval\]=np;  
    \}  
     else  
        free(( void\*)np->defn);  
     if((np->defn=strdup(defn))==NULL)  
         return NULL;  
     return np;  
\}  
void undef( char\*s)\{  
     int h;  
     struct nlist \*prev,\*np;  
    prev=NULL;  
    h=hash(s);  
     for(np=hashtab\[h\];np!=NULL;np=np->next)\{  
         if(strcmp(s,np->name)== 0)  
             break;  
        prev=np;  
    \}  
     if(np!=NULL)\{  
         if(prev==NULL)  
            hashtab\[h\]=np->next;  
         else  
            prev->next=np->next;  
        free(np->name);  
        free(np->defn);  
        free(np);  
    \}  
\}

![复制代码][copycode.gif]

![201208051120032341.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include < string.h>  
\#include <stdlib.h>  
\#include <ctype.h>  
\#define BUFSIZE 10                                   
char buf\[BUFSIZE\];                                   
int bufp= 0;                                          
int getch( void)\{                                     
     return bufp> 0?buf\[--bufp\]:getchar();             
\}                                                    
void ungetch( int c)\{                                 
     if(bufp>=BUFSIZE)                                
        printf( " ungetch: too many characters\\n ");    
     else                                             
        buf\[bufp++\]=c;                               
\}                                                    
void ungets( char \*s)\{  
     int len=strlen(s);  
     while(len> 0)  
        ungetch(s\[--len\]);  
\}  
char \*strdup\_( char \*s)\{  
     char \*p;  
    p=( char\*)malloc(strlen(s)+ 1);  
     if(p!=NULL)  
        strcpy(p,s);  
     return p;  
\}  
  
int comment( void)\{  
     int c;  
     while((c=getch())!=EOF)  
         if(c== ' \* ')  
             if((c=getch())== ' / ')  
                 break;  
             else  
                ungetch(c);  
     return c;  
\}  
int getword( char \*word, int lim)\{  
     char \*w=word;  
     int c,d;  
     while(isspace(c=getch()))  
        ;  
     if(c!=EOF)  
        \*w++=c;  
     if(isalpha(c)||c== ' \- '||c== ' \# ')\{  
         for(;--lim> 0;w++)  
             if(!isalnum(\*w=getch())&&\*w!= ' \- ')\{  
                ungetch(\*w);  
                 break;  
            \}  
    \}  
     else  if(c== ' \\' '||c== ' " ')\{  
         for(;--lim> 0;w++)  
             if((\*w=getch())== ' \\\\ ')  
                \*++w=getch();  
         else  if(\*w==c)\{  
            w++;  
             break;  
        \}  
         else  if(\*w==EOF)  
             break;  
              
    \}  
     else  if(c== ' / ')  
         if((d=getch())== ' \* ')  
            c=comment();  
     else  
        ungetch(d);  
    \*w= ' \\0 ';  
     return c;  
\}  
struct nlist\{  
     struct nlist \*next;  
     char \*name;  
     char \*defn;  
\};  
\#define HASHSIZE 101  
static  struct nlist \*hashtab\[HASHSIZE\];  
unsigned hash( char \*s)  
\{  
    unsigned hashval;  
     for(hashval= 0;\*s!= ' \\0 ';s++)  
        hashval=\*s+ 32\*hashval;  
     return hashval%HASHSIZE;  
\}  
struct nlist \*lookup( char \*s)\{  
     struct nlist \*np;  
     for(np=hashtab\[hash(s)\];np!=NULL;np=np->next)  
         if(strcmp(s,np->name)== 0)  
             return np;  
     return NULL;  
\}  
struct nlist \*install( char \*name, char\*defn)\{  
     struct nlist \*np;  
    unsigned hashval;  
     if((np=lookup(name))==NULL)\{  
        np=( struct nlist \*)malloc( sizeof( struct nlist));  
         if(np==NULL||(np->name=strdup\_(name))==NULL)  
             return NULL;  
        hashval=hash(name);  
        np->next=hashtab\[hashval\];  
        hashtab\[hashval\]=np;  
    \}  
     else  
        free(( void\*)np->defn);  
     if((np->defn=strdup\_(defn))==NULL)  
         return NULL;  
     return np;  
\}  
void undef( char\*s)\{  
     int h;  
     struct nlist \*prev,\*np;  
    prev=NULL;  
    h=hash(s);  
     for(np=hashtab\[h\];np!=NULL;np=np->next)\{  
         if(strcmp(s,np->name)== 0)  
             break;  
        prev=np;  
    \}  
     if(np!=NULL)\{  
         if(prev==NULL)  
            hashtab\[h\]=np->next;  
         else  
            prev->next=np->next;  
        free(np->name);  
        free(np->defn);  
        free(np);  
    \}  
\}  
  
void error( int c, char \*s)\{  
    printf( " error:%s\\n ",s);  
     while(c!=EOF&&c!= ' \\n ')  
        c=getch();  
\}  
void skipblanks()\{  
     int c;  
     while((c=getch())== '   '||c== ' \\t ')  
        ;  
    ungetch(c);  
\}  
\#define MAXWORD 100  
void getdef()\{  
     int c,i;  
     char def\[MAXWORD\],dir\[MAXWORD\],name\[MAXWORD\];  
    skipblanks();  
     if(!isalpha(getword(dir,MAXWORD)))  
        error(dir\[ 0\], " getdef:expecting a directive after \# ");  
     else  if(strcmp(dir, " define ")== 0)\{  
        skipblanks();  
         if(!isalpha(getword(name,MAXWORD)))  
            error(name\[ 0\], " getdef:non-alpha -name expected ");  
         else\{  
            skipblanks();  
             for(i= 0;i<MAXWORD- 1;i++)  
                 if((def\[i\]=getch())==EOF||  
                        def\[i\]== ' \\n ')  
                     break;  
            def\[i\]= ' \\0 ';  
             if(i<= 0)  
                error( ' \\n ', " getdef:incomplete define ");  
             else  
                install(name,def);  
        \}  
    \}  
     else  if(strcmp(dir, " undef ")== 0)\{  
        skipblanks();  
         if(!isalpha(getword(name,MAXWORD)))  
            error(name\[ 0\], " getdef:non-alpha in undef ");  
         else  
            undef(name);  
    \}  
     else  
        error(dir\[ 0\], " getdef:expecting a directive after \# ");  
\}  
  
int main()\{  
     char w\[MAXWORD\];  
     struct nlist \*p;  
     while(getword(w,MAXWORD)!=EOF)\{  
         if(strcmp(w, " \# ")== 0)  
            getdef();  
         else  if(!isalpha(w\[ 0\]))  
            printf( " %s ",w);  
         else  if((p=lookup(w))==NULL)  
            printf( " %s ",w);  
         else   
            ungets(p->defn);  
    \}  
     return  0;  
\}

![复制代码][copycode.gif]

![201208051120035339.png][]

第7章 输入与输出

变长参数列表

![201208051120046145.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdarg.h>  
  
void minprintf( char \*fmt,...)\{  
    va\_list ap;  
     char \*p,\*sval;  
     int ival;  
     double dval;  
    va\_start(ap,fmt);  
     for(p=fmt;\*p;p++)\{  
         if(\*p!= ' % ')\{  
            putchar(\*p);  
             continue;  
        \}  
         switch(\*++p)\{  
             case  ' d ':  
                ival=va\_arg(ap, int);  
                printf( " %d ",ival);  
                 break;  
             case  ' f ':  
                dval=va\_arg(ap, double);  
                printf( " %f ",dval);  
                 break;  
             case  ' s ':  
                 for(sval=va\_arg(ap, char\*);\*sval;sval++)   
                    putchar(\*sval);  
                 break;  
             default:  
                putchar(\*p);  
                 break;  
        \}  
    \}  
    va\_end(ap);  
\}  
int main()\{  
     int a= 3;  
     double d= 8.7;  
    minprintf( " %d %f\\n ",a,d);  
  
\}

![复制代码][copycode.gif]

![201208051120049177.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdarg.h>  
\#include <ctype.h>  
\#define LOCALFMT 100  
  
void minprintf( char \*fmt,...)\{  
    va\_list ap;  
     char \*p,\*sval;  
     char localfmt\[LOCALFMT\];  
     int ival,i;  
    unsigned uval;  
     double dval;  
    va\_start(ap,fmt);  
     for(p=fmt;\*p;p++)\{  
         if(\*p!= ' % ')\{  
            putchar(\*p);  
             continue;  
        \}  
        i= 0;  
        localfmt\[i++\]= ' % ';  
         while(\*(p+ 1)&&!isalpha(\*(p+ 1)))  
            localfmt\[i++\]=\*++p;  
        localfmt\[i++\]=\*(p+ 1);  
        localfmt\[i\]= ' \\0 ';  
         switch(\*++p)\{  
             case  ' d ':  
             case  ' i ':  
                ival=va\_arg(ap, int);  
                printf(localfmt,ival);  
                 break;  
             case  ' x ':  
             case  ' X ':  
             case  ' u ':  
             case  ' o ':  
                uval=va\_arg(ap,unsigned);  
                printf(localfmt,uval);  
             case  ' f ':  
                dval=va\_arg(ap, double);  
                printf(localfmt,dval);  
                 break;  
             case  ' s ':  
                sval=va\_arg(ap, char\*);  
                printf(localfmt,sval);  
                 break;  
             default:  
                putchar(\*p);  
                 break;  
        \}  
    \}  
    va\_end(ap);  
\}  
int main()\{  
     int a= 3;  
     double d= 8.7;  
    minprintf( " %d %f\\n ",a,d);  
  
\}

![复制代码][copycode.gif]

![201208051120047748.png][]

![201208051120042732.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdarg.h>  
\#include <ctype.h>  
\#define LOCALFMT 100  
void minscanf( char \*fmt,...)\{  
    va\_list ap;  
     char \*p,\*sval;  
     char localfmt\[LOCALFMT\];  
     int c,i,\*ival;  
    unsigned \*uval;  
     double \*dval;  
    va\_start(ap,fmt);  
     for(p=fmt;\*p;p++)\{  
         if(\*p!= ' % ')\{  
            localfmt\[i++\]=\*p;  
             continue;  
        \}  
        i= 0;  
        localfmt\[i++\]= ' % ';  
         while(\*(p+ 1)&&!isalpha(\*(p+ 1)))  
            localfmt\[i++\]=\*++p;  
        localfmt\[i++\]=\*(p+ 1);  
        localfmt\[i\]= ' \\0 ';  
         switch(\*++p)\{  
             case  ' d ':  
             case  ' i ':  
                ival=va\_arg(ap, int\*);  
                scanf(localfmt,ival);  
                 break;  
             case  ' x ':  
             case  ' X ':  
             case  ' u ':  
             case  ' o ':  
                uval=va\_arg(ap,unsigned\*);  
                scanf(localfmt,uval);  
                 break;  
             case  ' f ':  
                dval=va\_arg(ap, double\*);  
                scanf(localfmt,dval);  
                 break;  
             case  ' s ':  
                sval=va\_arg(ap, char\*);  
                scanf(localfmt,sval);  
                 break;  
             default:  
                scanf(localfmt);  
                 break;  
        \}  
    \}  
\}

![复制代码][copycode.gif]

![201208051120059667.png][]

![201208051120053222.png][]

下面是标准库中对fgets和fputs函数的实现：

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

char \*fgets( char \*s, int n,FILE\*iop)\{  
    register  int c;  
    register  char \*cs;  
    cs=s;  
     while(--n> 0&&(c=getc(iop))!=EOF)  
         if((\*cs++=c)== ' \\n ')  
             break;  
    \*cs= ' \\0 ';  
     return (c==EOF&&cs==s)?NULL:s;  
\}    
int fputs( char\*s ,FILE\*iop)\{  
     int c;  
     while(c=\*s++)  
        putc(c,iop);  
     return ferror(ip)?EOF: 0;                 
\}

![复制代码][copycode.gif]

![201208051120052666.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
\#include < string.h>  
\#define MAXLINE 100  
void filecomp(FILE\*fp1,FILE\*fp2)\{  
     char line1\[MAXLINE\],line2\[MAXLINE\];  
     char\*lp1,\*lp2;  
     do\{  
        lp1=fgets(line1,MAXLINE,fp1);  
        lp2=fgets(line2,MAXLINE,fp2);  
         if(lp1==line1&&lp2==line2)\{  
             if(strcmp(line1,line2)!= 0)\{  
                printf( " first difference in line\\n %s\\n ",line1);  
                lp1=lp2=NULL;  
            \}  
        \}  
         else  if(lp1!=line1&&lp2==line2)  
            printf( " end of first at line\\n%s\\n ",line2);  
         else  if(lp1==line1&&lp2!=line2)  
            printf( " end of first at line\\n%s\\n ",line1);  
    \}  
     while(lp1==line1&&lp2==line2);  
\}  
int main( int argc, char \*argv\[\])\{  
    FILE \*fp1,\*fp2;  
     if(argc!= 3)\{  
        fprintf(stderr, " comp:need two file names\\n ");  
        exit( 1);  
    \}  
     else\{  
         if((fp1=fopen(\*++argv, " r "))==NULL)\{  
            fprintf(stderr, " comp:can't open %s\\n ",\*argv);  
            exit( 1);  
        \}  
         else  if((fp2=fopen(\*++argv, " r "))==NULL)\{  
            fprintf(stderr, " comp:can't open %s\\n ",\*argv);  
            exit( 1);  
        \}  
         else\{  
            filecomp(fp1,fp2);  
            fclose(fp1);  
            fclose(fp2);  
            exit( 0);  
        \}  
    \}  
\}

![复制代码][copycode.gif]

![201208051120057649.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include < string.h>  
\#include <stdlib.h>  
\#define MAXLINE 1000  
void fpat(FILE \*fp, char \*fname, char \*pattern, int except, int number);  
int main( int argc, char\*argv\[\])\{  
     char pattern\[MAXLINE\];  
     int c,except= 0,number= 0;  
    FILE \*fp;  
     while(--argc> 0&&(\*++argv)\[ 0\]== ' \- ')  
         while(c=\*++argv\[ 0\])  
             switch(c)\{  
                 case  ' x ':  
                    except= 1;  
                     break;  
                 case  ' n ':  
                    number= 1;  
                     break;  
                 default:  
                    printf( " find:illegal option %c\\n ",c);  
                    argc= 0;  
                     break;  
            \}  
     if(argc>= 1)  
        strcpy(pattern,\*argv);  
     else\{  
        printf( " Usage:find \[-x\] \[-n\] pattern \[file ..\]\\n ");  
        exit( 1);  
    \}  
     if(argc== 1)  
        fpat(stdin, "",pattern,except,number);  
     else  
         while(--argc> 0)  
             if((fp=fopen(\*++argv, " r "))==NULL)\{  
                fprintf(stderr, " find: can't open %s\\n ",\*argv);  
                exit( 1);  
            \} else\{  
                fpat(fp,\*argv,pattern,except,number);  
                fclose(fp);  
            \}  
     return  0;  
\}  
void fpat(FILE \*fp, char \*fname, char \*pattern, int except, int number)\{  
     char line\[MAXLINE\];  
     long lineno= 0;  
     while(fgets(line,MAXLINE,fp)!=NULL)\{  
        ++lineno;  
         if((strstr(line,pattern)!=NULL)!=except)\{  
             if(\*fname)  
                printf( " %s -  ",fname);  
             if(number)  
                printf( " %ld:  ",lineno);  
            printf( " %s ",line);  
        \}  
    \}  
\}

![复制代码][copycode.gif]

![201208051120058488.png][]

![201208051120061520.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include <stdlib.h>  
  
\#define MAXBOT 3  
\#define MAXHDR 5  
\#define MAXLINE 100  
\#define MAXPAGE 66  
int heading( char \*fname, int pageno)\{  
     int ln= 3;  
    fprintf(stdout, " \\n\\n ");  
    fprintf(stdout, " %s   page %d\\n ",fname,pageno);  
     while(ln++<MAXHDR)  
        fprintf(stdout, " \\n ");  
     return ln;  
\}  
void fileprint(FILE\*fp, char \*fname)\{  
     int lineno,pageno= 1;  
     char line\[MAXLINE\];  
    lineno=heading(fname,pageno++);  
     while(fgets(line,MAXLINE,fp)!=NULL)\{  
         if(lineno== 1)\{  
            fprintf(stdout, " \\f ");  
            lineno=heading(fname,pageno++);  
        \}  
        fputs(line,stdout);  
         if(++lineno>MAXPAGE-MAXBOT)  
            lineno= 1;  
    \}  
    fprintf(stdout, " \\f ");  
\}  
int main( int argc, char \*argv\[\])\{  
    FILE \*fp;  
     if(argc== 1)  
        fileprint(stdin, "   ");  
     else  
         while(--argc> 0)  
             if((fp=fopen(\*++argv, " r "))==NULL)\{  
                fprintf(stderr, " print:can't open %s\\n ",\*argv);  
                exit( 1);  
            \}  
             else\{  
                fileprint(fp,\*argv);  
                fclose(fp);  
            \}  
     return  0;  
\}

![复制代码][copycode.gif]

![201208051120069535.png][]

随机数发生器，生成浮点数的方法

![201208051120065599.png][]

第8章 UNIX系统接口

![201208051120068389.png][]

利用低级的read和write函数来构造高级函数getchar，putchar等。

![复制代码][copycode.gif]

int getchar\_( void)\{  
     char c;  
     return (read( 0,&c, 1)== 1)?(unsigned  char)c:EOF;  
\}    
int getchar\_\_( void)\{  
     static  char buf\[BUFSIZ\];  
     static  char \*bufp=buf;  
     static  int n= 0;  
     if(n== 0)\{  
        n=read( 0,buf, sizeof buf);  
        bufp=buf;  
    \}  
     return (--n> 0)?(unsigned  char )\*bufp++:EOF;       
  
\}

![复制代码][copycode.gif]

![201208051120071944.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <unistd.h>  
\#define NULL 0  
\#define EOF (-1)  
\#define BUFSIZ 1024  
\#define OPEN\_MAX 20  
typedef  struct \_iobuf\{  
     int cnt;  
     char \*ptr;  
     char \* base;  
     int flag;  
     int fd;  
\}FILE;  
extern FILE \_iob\[OPEN\_MAX\];  
\#define stdin (&\_iob\[0\])  
\#define stdout (&\_iob\[1\])  
\#define stderr (&\_iob\[2\])  
enum \_flags\{  
    \_READ = 01,  
    \_WRITE = 02,  
    \_UNBUF= 04,  
    \_EOF = 010,  
    \_ERR= 020  
\};  
int \_fillbuf(FILE\*);  
int \_flushbuf( int ,FILE \*);  
\#define feof(p) (((p)->flag&\_EOF)!=0)  
\#define ferror(p) (((p)->flag&\_ERR)!=0)  
\#define fileno(p) ((p)->fd)  
  
\#define getc(p) (--(p)->cnt>=0\\  
        ?(unsigned  char)\*(p)->ptr++:\_fillbuf(p))  
  
\#define putc(x,p) (--(p)->cnt>=0\\  
        ?\*(p)->ptar++=(x):\_flushbuf((x),p))  
  
\#define getchar() getc(stdin)  
\#define putchar(x) putc(x,stdout)  
  
\#include <fcntl.h>  
\#define PERMS 0666  
FILE \*fopen( char \*name, char \*mode)  
\{  
     int fd;  
    FILE \*fp;  
     if(\*mode!= ' r '&&\*mode!= ' w '&&\*mode!= ' a ')  
         return NULL;  
     for(fp=\_iob;fp<\_iob+OPEN\_MAX;fp++)  
         if((fp->flag&(\_READ|\_WRITE))== 0)  
             break;  
     if(fp>=\_iob+OPEN\_MAX)  
         return NULL;  
     if(\*mode== ' w ')  
        fd=creat(name,PERMS);  
     else  if(\*mode== ' a ')\{  
         if((fd=open(name,O\_WRONLY, 0))==- 1)  
            fd=creat(name,PERMS);  
        lseek(fd, 0L, 2);  
    \}  
     else  
        fd=open(name,O\_RDONLY, 0);  
     if(fd==- 1)  
         return NULL;  
    fp->fd=fd;  
    fp->cnt= 0;  
    fp-> base=NULL;  
    fp->flag=(\*mode== ' r ')?\_READ:\_WRITE;  
     return fp;  
\}  
  
int \_fillbuf(FILE\*fp)\{  
     int bufsize;  
     if((fp->flag&(\_READ|\_EOF|\_ERR))!=\_READ)  
         return EOF;  
    bufsize=(fp->flag&\_UNBUF)? 1:BUFSIZ;  
     if(fp-> base==NULL)  
         if((fp-> base=( char\*)malloc(bufsize))==NULL)  
             return EOF;  
    fp->ptr=fp-> base;  
    fp->cnt=read(fp->fd,fp->ptr,bufsize);  
     if(--fp->cnt< 0)\{  
         if(fp->cnt==- 1)  
            fp->flag|=\_EOF;  
         else  
            fp->flag|=\_ERR;  
        fp->cnt= 0;  
         return EOF;  
    \}  
     return (unsigned  char)\*fp->ptr++;  
\}  
FILE \_iob\[OPEN\_MAX\]=\{  
    \{ 0,( char\*) 0,( char\*) 0,\_READ, 0 \},  
    \{ 0,( char\*) 0,( char\*) 0,\_WRITE, 1 \},  
    \{ 0,( char\*) 0,( char\*) 0,\_WRITE|\_UNBUF, 2 \},  
\};  
int \_flushbuf( int x,FILE\*fp)\{  
    unsigned nc;  
     int bufsize;  
     if(fp<\_iob||fp>=\_iob+OPEN\_MAX)  
         return EOF;  
     if((fp->flag&(\_WRITE|\_ERR))!=\_WRITE)  
         return EOF;  
    bufsize=(fp->flag&\_UNBUF)? 1:BUFSIZ;  
     if(fp-> base==NULL)\{  
         if((fp-> base=( char\*)malloc(bufsize))==NULL)\{  
            fp->flag|=\_ERR;  
             return EOF;  
        \}  
    \}  
     else\{  
        nc=fp->ptr-fp-> base;  
         if(write(fp->fd,fp-> base,nc)!=nc)\{  
            fp->flag|=\_ERR;  
             return EOF;  
        \}  
    \}  
    fp->ptr=fp-> base;  
    \*fp->ptr++=( char)x;  
    fp->cnt=bufsize- 1;  
     return x;  
\}  
int fclose(FILE \*fp)\{  
     int rc;  
     if((rc=fflush(fp))!=EOF)\{  
        free(fp-> base);  
        fp->ptr=NULL;  
        fp->cnt= 0;  
        fp-> base=NULL;  
        fp->flag&=(\_READ|\_WRITE);  
    \}  
     return rc;  
\}  
int fflush(FILE\*fp)\{  
     int rc= 0;  
     if(fp<\_iob||fp>=\_iob+OPEN\_MAX)  
         return EOF;  
     if(fp->flag&\_WRITE)  
        rc=\_flushbuf( 0,fp);  
    fp->ptr=fp-> base;  
    fp->cnt=(fp->flag&\_UNBUF)? 1:BUFSIZ;  
     return rc;  
\}  
  
int fseek(FILE \*fp, long offset, int origin)\{  
    unsigned nc;  
     long rc= 0;  
     if(fp->flag&\_READ)\{  
         if(origin== 1)  
            offset-=fp->cnt;  
        rc=lseek(fp->fd,offset,origin);  
        fp->cnt= 0;  
    \}  
     else  if(fp->flag&\_WRITE)\{  
         if((nc=fp->ptr-fp-> base)> 0)  
             if(write(fp->fd,fp-> base,nc)!=nc)  
                rc=- 1;  
         if(rc!=- 1)  
            rc=lseek(fp->fd,offset,origin);  
    \}  
     return (rc==- 1)?- 1: 0;  
\}

![复制代码][copycode.gif]

![201208051120079403.png][]

![20120805112008766.png][]

![201208051120084877.png][]

![201208051120088224.png][]

![201208051120081223.png][]

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

\#include <stdio.h>  
\#include < string.h>  
\#include <fcntl.h>  
\#include <sys/types.h>  
\#include <sys/stat.h>  
\#include <dirent.h>  
  
// \#define NAME\_MAX 14  
 // typedef struct\{  
 //     long ino;  
 //     char name\[NAME\_MAX+1\];  
 // \}Dirent;  
 // typedef struct\{  
 //     int fd;  
 //     Dirent d;  
 // \}DIR;  
 // DIR \*opendir(char \*dirname);  
 // Dirent\* readdir(DIR\*dfd);  
 // void closedir(DIR\* dfd);  
  
 // char \*name;  
 // struct stat stbuf;  
 // int stat(char \*,struct stat\*);  
 // \#define S\_IFMT 0160000  
 // \#define S\_IFDIR 0040000  
 // \#define S\_IFCHR 0020000  
 // \#define S\_IFBLK 0060000  
 // \#define S\_IFREG 001000   
 \#define MAX\_PATH 1024  
  
void dirwalk( char \*dir, void(\*fcn)( char\*))\{  
     char name\[MAX\_PATH\];  
     struct dirent \*dp;  
    DIR \*dfd;  
     if((dfd=opendir(dir))==NULL)\{  
        fprintf(stderr, " dirwalk:can't open %s\\n ",dir);  
         return;   
    \}  
     while((dp=readdir(dfd))!=NULL)\{  
         if(strcmp(dp->d\_name, " . ")== 0||  
                strcmp(dp->d\_name, " .. ")== 0)  
             continue;  
         if(strlen(dir)+strlen(dp->d\_name)+ 2> sizeof(name))  
            fprintf(stderr, " dirwalk:name %s %s too long\\n ",  
                    dir,dp->d\_name);  
         else\{  
            sprintf(name, " %s/%s ",dir,dp->d\_name);  
            fcn(name);  
        \}  
    \}  
    closedir(dfd);  
\}  
  
void fsize( char \*name)\{  
     struct stat stbuf;  
     if(stat(name,&stbuf)==- 1)\{  
        fprintf(stderr, " fsize:can't access %s\\n ",name);  
         return ;  
    \}  
     if((stbuf.st\_mode&S\_IFMT)==S\_IFDIR)  
        dirwalk(name,fsize);  
    printf( " %5u %6o %3u %8ld %s\\n ",stbuf.st\_ino,  
            stbuf.st\_mode,stbuf.st\_nlink,stbuf.st\_size,name);  
\}  
int main( int argc, char \*\*argv)\{  
     if(argc== 1)  
        fsize( " . ");  
     else  
         while(--argc> 0)  
            fsize(\*++argv);  
     return  0;  
\}

![复制代码][copycode.gif]

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![复制代码][copycode.gif]

typedef  long Align;  
union header\{  
     struct \{  
        union header \*ptr;  
        unsigned size;  
    \}S;  
    Align x;  
\};  
typedef union header Header;  
static Header  base;  
static Header \*freep=NULL;  
void \*malloc(unsigned nbytes)\{  
    Header \*p,\*prevp;  
    Header \*moreroce(unsigned);  
    unsigned nuints;  
    nuints=(nbytes+ sizeof(Header)- 1)/ sizeof(header)+ 1;  
     if((prevp=freep)==NULL)\{  
         base.s.ptr=freeptr=prevptr=& base;  
         base.s.size= 0;  
    \}  
     for(p=prevp->s.ptr;;prevp=p,p=p->s.ptr)\{  
         if(p->s.size>=nuints)\{  
             if(p->s.size==nuints)  
                prevp->s.ptr=p->s.ptr;  
             else\{  
                p->s.size-=nuints;  
                p+=p->s.size;  
                p->s.size=nuints;  
            \}  
            freep=prevp;  
             return ( void\*)(p+ 1);  
        \}  
         if(p==freep)  
             if((p=moreroce(nuints))==NULL)  
                 return NULL;  
    \}  
\}  
\#define NALLOC 1024  
static Header \*moreroce(unsigned nu)\{  
     char \*cp,\*sbrk( int);  
    Header \*up;  
     if(nu<NALLOC)  
        nu=NALLOC;  
    cp=sbrk(nu\* sizeof(Header));  
     if(cp==( char\*)- 1)  
         return NULL;  
    up=(Header\*)cp;  
    up->s.size=nu;  
    free(( void\*)(up+ 1));  
     return freep;  
\}  
void free( void\*ap)\{  
    Header \*bp,\*p;  
    bp=(Header\*)ap- 1;  
     for(p=freep;!(bp>p&&bp<p->s.ptr);p=p->s.ptr)  
         if(p>=p->s.ptr&&(bp>p||bp<p->s.ptr))  
             break;  
     if(bp+bp->size==p->s.ptr)\{  
        bp->s.size+=p->s.ptr->s.size;  
        bp->s.ptr=p->s.ptr->s.ptr;  
    \}  
     else  
        bp->s.ptr=p->s.ptr;  
     if(p+p->size==bp)\{  
        p->s.size+=bp->s.size;  
        p->s.ptr=bp->s.ptr;  
    \}  
     else  
        p->s.ptr=bp;  
    freep=p;  
\}  
void \*calloc(unsigned n,unsigned size)\{  
    unsigned i,nb;  
     char \*p,\*q;  
    nb=n\*size;  
     if((p=q=malloc(nb))!=NULL)  
         for(i= 0;i<nb;i++)  
            \*p++= 0;  
     return q;  
\}

![复制代码][copycode.gif]

[http_www.cnblogs.com_xkfz007_articles_2566424.html]: http://www.cnblogs.com/xkfz007/articles/2566424.html
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[http_cdecl.org]: http://cdecl.org/
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