字符转整数算法-蒲公英云

字符转整数算法

快来打我* 2022-06-09 00:20 141阅读 0赞

把一个字符串转成整数：

StrToInt.cpp

#include
using namespace std;

long long strToInt(const char* str)
{
long long num = 0;
bool minus = false;
cout << “befor To int :” << str << endl;
if(str != NULL && *str != ‘\0’){
if(*str == ‘+’){
str++;
minus = false;
}

if(*str == ‘-‘){
str++;
minus = true;
}

while(*str != ‘\0’){
if(*str >= ‘0’ && *str <=’9’){
int flag = minus ? -1 : 1;

//核心语句就这句，其他都是健壮性处理

num = num*10 + flag*(*str - ‘0’);

//是否超出范围
if((!minus && num >0x7FFFFFFF) || (minus && (signed int)num <0x80000000)){
num =0;
cout << “the range of number invalid! \n”;
break;
}
str++;
}else{
num = 0;
cout << “the char of num invalid!\n”;
break;
}
}
}

cout << “after to Int :” << num << endl;
return num;
}

int main(){

//测试

strToInt(“123”);
strToInt(“-123”);
strToInt(“123aaa”);
strToInt(“”);
strToInt(“123456789”);
strToInt(“123999999999999999999999999999999999999”);
return 0;
}

测试结果：

PC:~/algorithm$ g++ StrToInt.cpp -o StrToInt
PC:~/algorithm$ ./StrToInt
befor To int :123
after to Int :123
befor To int :-123
after to Int :-123
befor To int :123aaa
the char of num invalid!
after to Int :0
befor To int :
after to Int :0
befor To int :123456789
after to Int :123456789
befor To int :123999999999999999999999999999999999999
the range of number invalid!
after to Int :0