PAT A1001 A+B Format

1001A+B Format（20 分）

Calculatea+band 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 integersaandbwhere−106≤a,b≤106. The numbers are separated by a space.

Output Specification:

For each test case, you should output the sum ofaandbin one line. The sum must be written in the standard format.

Sample Input:

-1000000 9

Sample Output:

-999,991

#include<iostream>
#include<cstdio>
#include <cstring>
using namespace std;
int main(){
  int a,b,c;
  char str[10],str2[10];
  cin>>a>>b;
  c=a+b;
  sprintf(str,"%d",c);
  int len=strlen(str);
  int index=0,k=0;
  for(int i=len-1;i>=0;i--){
    if(k!=0&&k%3==0&&!(i==0&&!isdigit(str[i]))) str2[index++]=',';
    str2[index++]=str[i];
    k++;
  }
  for(int i=index-1;i>=0;i--){
    cout<<str2[i];
  }
  cout<<endl;
  return 0;
}