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");}