1001 A+B Format (20分) 题解，易错点分析

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​​≤a,b≤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

拓展点 ：题目中的标准格式是三位分节法，是从右往左，每三位用逗号分开，如果正常从左往右每三位用逗号分开，就会有好几个测试点过不去，如-1000，应该是-1,000。

 

代码：

#include <bits/stdc+