atoi 与 itoa的实现

//atoi的实现#include<iostream>using namespace std;int atio1(char *s){int sign=1,num=0; if(*s=='-') sign=-1; s++; while((*s)!='\0') { num=num*10+(*s-'0'); s++; } return num*sign; } //itoa的实现char *itoa(int num, char *str, int radix)
{
char* ptr = str;
int i;
int j;

while (num)
{
*ptr++ = string[num % radix];
num /= radix;

if (num < radix)
{
*ptr++ = string[num];
*ptr = '\0';
break;
}
}

j = ptr - str - 1;

for (i = 0; i < (ptr - str) / 2; i++)
{
int temp = str[i];
str[i] = str[j];
str[j--] = temp;
}

return str;
}
int main(){ char *s="-123567890"; cout<<atio1(s); system("pause");}