题目
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 Specification:：
Each input file contains one test case. Each case contains a pair of integers a and b where − 1 0 6 ⩽ a , b ⩽ 1 0 6 -10^6\leqslant a,b\leqslant 10^6 −106⩽a,b⩽106 . The numbers are separated by a space.
Output Specification:
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
思路分析：
利用string类的to_string函数将int类型转换为string类型
代码：
#include <iostream>
using namespace std;
int main(){
int a, b;
cin >> a >> b;
string s = to_string(a + b), res;
for(int i = s.size() - 1, j = 1; i >= 0; i--, j++){
res = s[i] + res;
if(j % 3 == 0 && i && s[i - 1] != '-') res = "," + res;
}
cout << res << endl;
}