PAT (Advanced Level) Practice 1001 A+B Format

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 −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

---

#include<bits/stdc++.h> 
using namespace std;
string out(int num);
int main()
{
	int a,b;
	while(cin>>a>>b)
	{
		cout<<out(a+b)<<endl;	
	}	
	return 0;
}
string out(int num)
{
	char number[]={'0','1','2','3','4','5','6','7','8','9'};
	string ret,s;
	int count; 
	ret="";
	s="";
	count=0;
	if(num<0)//注意结果小于零的情况
	{
		s="-";
		num=0-num;
	}
	if(num==0)//注意结果为零的情况
	{
		return "0";
	}
	while(num)
	{
		int temp;
		temp=num%10;
		count++;
		num=num/10;
		if(count==3&&num!=0)//注意刚好是三个数的情况 
		{
			ret=number[temp]+ret;
			ret=","+ret;
			count=0;
		}
		else
		{
			ret=number[temp]+ret;
		}
		
	}
	return s+ret;
}