1001. A+B Format (20)

#include <iostream>#include <cstdio>#include <cmath>using namespace std;string toString(int num){    if(num == 0) return string("0");    string s;    int flag = 0;    while(num){        s = char(num % 10 + '0') + s;        num /= 10;        ++flag;        if(flag == 3 && num){            flag = 0;            s = "," + s;        }    }    return s;}int main(){int a, b;scanf("%d%d", &a, &b);int sum = a + b;int flag = 0;    if(sum < 0) printf("-");    string s = toString(abs(sum));    printf("%s", s.c_str());return 0;}