6-4 链式表的按序号查找 (10 分)

痛定思痛。 2022-08-28 05:46 124阅读 0赞

> 本题要求实现一个函数，找到并返回链式表的第K个元素。

## 函数接口定义： ##

ElementType FindKth( List L, int K );

> 其中List结构定义如下：

typedef struct LNode *PtrToLNode;
    struct LNode { 
        ElementType Data;
        PtrToLNode Next;
    };
    typedef PtrToLNode List;

L是给定单链表，函数FindKth要返回链式表的第K个元素。如果该元素不存在，则返回ERROR。

## 裁判测试程序样例： ##

#include <stdio.h>
    #include <stdlib.h>
    
    #define ERROR -1
    typedef int ElementType;
    typedef struct LNode *PtrToLNode;
    struct LNode { 
        ElementType Data;
        PtrToLNode Next;
    };
    typedef PtrToLNode List;
    
    List Read(); /* 细节在此不表 */
    
    ElementType FindKth( List L, int K );
    
    int main()
    { 
        int N, K;
        ElementType X;
        List L = Read();
        scanf("%d", &N);
        while ( N-- ) { 
            scanf("%d", &K);
            X = FindKth(L, K);
            if ( X!= ERROR )
                printf("%d ", X);
            else
                printf("NA ");
        }
        return 0;
    }
    
    /* 你的代码将被嵌在这里 */

## 输入样例： ##

1 3 4 5 2 -1
    6
    3 6 1 5 4 2

## 输出样例： ##

4 NA 1 2 5 3

## AC: ##

ElementType FindKth( List L, int K ){ 
        int x = 1;
        if(K <= 0)
            return -1;
            while(L!=NULL){ 
                if(x == K){ 
                    return L->Data;
                }
                x++;
                L = L->Next;
            }
            return -1;
    }

--------------------

## WA: ##

ElementType FindKth( List L, int K ){ 
        int x = 0;
        if(K <= 0)
            return -1;
            while(L!=NULL){ 
                x++;
                L = L->Next;
                if(x == K){ 
                    return L->Data;
                }
            }
            return -1;
    }

![WA][]

> a.c: In function ‘FindKth’:  
> a.c:56:5: warning: this ‘if’ clause does not guard… \[-Wmisleading-indentation\]  
> if(K <= 0)  
> ^~  
> a.c:58:9: note: …this statement, but the latter is misleadingly indented as if it is guarded by the ‘if’  
> while(L!=NULL)\{  
> ^~~~~  
> a.c: In function ‘Read’:  
> a.c:20:2: warning: ignoring return value of ‘scanf’, declared with attribute warn\_unused\_result \[-Wunused-result\]  
> scanf("%d", &X);  
> ^~~~~~~~~~~~~~~  
> a.c:28:3: warning: ignoring return value of ‘scanf’, declared with attribute warn\_unused\_result \[-Wunused-result\]  
> scanf("%d", &X);  
> ^~~~~~~~~~~~~~~  
> a.c: In function ‘main’:  
> a.c:40:5: warning: ignoring return value of ‘scanf’, declared with attribute warn\_unused\_result \[-Wunused-result\]  
> scanf("%d", &N);  
> ^~~~~~~~~~~~~~~  
> a.c:42:9: warning: ignoring return value of ‘scanf’, declared with attribute warn\_unused\_result \[-Wunused-result\]  
> scanf("%d", &K);  
> ^~~~~~~~~~~~~~~

--------------------

[WA]: /images/20220828/fab2f381746449f087da5ccef8c44815.png