1001 A+B Format (20分)  

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 −. 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

长度余3的地方插进去一个逗号，正数的话i要加1，负号占了一个下标不用加。数字的最后面和最前面也不用加逗号。

#include<bits/stdc++.h> using namespace std; #define _for(i, a, b) for (int i = (a); i <= (b); i++) int main() {     char s[15], rs[15];     int a, b, c;     cin >> a >> b;     c = a + b;     sprintf(s,"%d",c);     int len = strlen(s);     for (int i = 0; i < len;i++){         printf("%c", s[i]);         if(s[0]=='-'){             if((i)%3==(len-1)%3&&i!=len-1&&i!=0){                 printf(",");             }         }else{             if ((i+1) % 3 == len % 3 && i != len - 1)             {                 printf(",");             }         }     }     puts("");     return 0; }