[PAT甲级]1001. A+B Format (20)(AB和的标准输出)

1001. A+B Format (20)

原题链接

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

题目大意：

• 输入两个数a,b，输出它们的和
• 最后的输出按照标准输出，从右往左每3个数字加一个逗号

代码：

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

int main()
{
    int a,b;
    cin >> a >> b;
    int sum = a + b;
    string res="";
    bool flag = true;//正数
    if(sum < 0){
        flag = false;
        sum = -sum;
    }
    int t=0;
    do{
        if(t == 3){
            res = ',' + res;
            t = 0;
        }
        char c = sum%10+'0';
        res = c + res;
        t++;
        sum /= 10;
    }while(sum != 0);
    if(!flag)
        res = '-' + res;
    cout << res;
    return 0;
}