把字符串“123456”转换成数值123456
#include "head.h"
int main(int argc, const char *argv[])
{
char a[20]="123456";
printf("%d\n",atoi(a));
return 0;
}
#ifndef N
#define N
#include <stdio.h>
int atoi(char *str);
#endif
#include "head.h"
#include <stdio.h>
int atoi(char *str)
{
int sum=0;
while(*str)
{
sum=sum*10+(*str-'0');
str++;
}
return sum;
}