字符串和整数的相互转换

#include <iostream>
#include <string>
using namespace std;

int myatoi(const char *s) {//字符串转换成整数
    int i, sign, num;
    for(i = 0; isspace(s[i]); i++);//跳过字符串前面的空格

    if (s[i] == '-')
        sign = -1;
    else
        sign = 1;

    if(s[i] == '-' || s[i] == '+') i++;//符号位

    for(num = 0; isdigit(s[i]); i++) {//遇到非数字字符就结束循环
        num = 10 * num + s[i] - '0';
    }
    return sign * num;
}

void reverse(char *s) {
    char *p = s;
    int len = 0;
    while(*p++ != '\0') len++;
    for(int i = 0, j = len-1; i <=j; i++, j--) {
        s[i] = s[i] ^ s[j];
        s[j] = s[i] ^ s[j];
        s[i] = s[i] ^ s[j];
    }
}

void myitoa(int num, char *s) {//整数置换成字符串
    int sign = 1;
    if(num < 0) {
        num = -num;
        sign = -1;
    }

    int i = 0;
    do{
        s[i++] = num % 10 + '0';
        num /= 10;
    }while(num > 0);

    if(sign == -1)
        s[i++] = '-';
    s[i] = '\0';

    reverse(s);

}

int main() {
    char str[] = "   -1234567a8";
    int num = -1234567;

    cout << myatoi(str) << endl;
    myitoa(num, str);
    cout << str << endl;

    return 0;
}