PAT| 1001. A+B Format

Calculate a + b and output the sum in standard format – that is, the
digits must be separated into groups of three by commas (unless there
are less than four digits).

Input

Each input file contains one test case. Each case contains a pair of
integers a and b where -1000000 <= a, b <= 1000000. The numbers are
separated by a space.

Output

For each test case, you should output the sum of a and b in one line.
The sum must be written in the standard format.

Sample Input
-1000000 9 Sample Output
-999,991
链接

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<stdio.h>
#include<string>
using namespace std;
int main()
{
    int a, b;
    while (scanf("%d%d",&a,&b)!=EOF)
    {
        int sum = a + b;
        string s;

        //如果是负数
        if (sum < 0)
        {
            printf("-");
            sum *= -1;
        }
        int cur = 0;
        do
        {
            int r = sum % 10;
            sum /= 10;
            if (cur < 3)
            {
                s.insert(s.begin(), r + '0');
                cur++;
            }
            else
            {
                s.insert(s.begin(), ',');
                s.insert(s.begin(), r + '0');
                cur = 1;
            }

        } while (sum > 0);
        cout << s << endl;
    }
}