【PAT Advanced Level】1001. A+B Format (20)

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

int main()
{

int a,b;
cin>>a>>b;
int c = a + b;
stringstream strStream;
strStream<<c;			//int转string的方法！
string s = strStream.str();

for(int i = s.size() - 3; i > 0 && s[i - 1] != '-'; i -= 3)
s.insert(i, ",");

cout<<s<<endl;
}