浙江大学PAT上机题解析之1001. A+B Format (20) 1001. A+B Format (20)

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

Each input file contains one test case.  Each case contains a pair of integers a and b where -1000000 <= a, b <= 1000000.  The numbers are separated by a space.

Output

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.

-1000000 9

-999,991

#include<iostream>
#include <string>
#include <algorithm>

using namespace std;

int main()
{

  int M,N,sum=0;
  string  str;
  int flag=0;
  string::iterator it;
  cin>>M>>N;
  sum = M+N;
  if (sum<0)
  {
    sum  = 0-sum;
    flag=1;
  }

  while(sum)
  {
    char  ch = '0'+sum%10;

    str.push_back(ch);

    sum/=10;

  }
  if (str.empty())
  cout<<"0"<<endl;
  if (flag)
  cout<<"-";
  reverse(str.begin(),str.end());
  if (!str.empty()&&str.size()<=3)
  {
    cout<<str;
  }
  else
  {
   int num = str.size()%3;

   if (num==1)
   {
     cout<<*str.begin()<<",";
   }
   else
  if (num==2)
  {
    cout<<*str.begin()<<*(str.begin()+1)<<",";
  }
   int k=1;

   for (it=str.begin()+num;it!=str.end();it++)
   {
     if (k==4)
     {
       cout<<",";
       k=1;
     }
     cout<<*it;
     k++;
   }

  }

  cout<<endl;


//  system("pause");
  return 0;
}