题目链接：A+B Format (20分)

题目描述

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 $-10{}^6\le a,b\le 10^6$. 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

满分代码

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

int main()
{
	int a,b,sum;
	string s;
	cin>>a>>b;
	sum = a+b;
	
	s = to_string(sum);
	int len = s.length();
	for(int i=0;i<len;i++)
	{
		cout<<s[i];
		
		if (s[i] == '-') 
			continue;
 		if ((i + 1) % 3 == len % 3 && i != len - 1) 
		 	cout << ",";
	}

	return 0;
} 

说明：这个题主要就是加逗号的位置，从右向左每3各数要加一个逗号，用模运算处理，比较简单