**
关于atoi函数的实现
#include <stdio.h>
#include<stdlib.h>
#include<assert.h>
int atoi(char * str)
{
assert(str);
int flag = 1;
if (*str == ‘-’)
{
++str;
flag == -1;
}
else if (*str == ‘+’)
{
++str;
}
int num = 0;
while ( *str !=’\0’)
{
if (*str > ‘9’ || *str < ‘0’)
{
printf(“非法字符”);
return -1;
}
num *= 10;
num += (str - ‘0’);
++str;
}
return numflag;
}
int main()
{
printf("%d\n", atoi(“186”));
printf("%d\n", atoi("-186"));
printf("%d\n", atoi("+186"));
printf("%d\n", atoi(“18a6”));
system(“pause”);
return 0;
}
**