关键函数：
to_string
string转int :int number = std::atoi( text.c_str() );
代码实现：
#include <iostream>
#include <string>
using namespace std;
int main() {
int a, b;
cin >> a >> b;
string s = to_string(a + b);
int len = s.length();
for (int i = 0; i < len; i++) {
cout << s[i];
if (s[i] == '-') continue;
if ((i + 1) % 3 == len % 3 && i != len - 1) cout << ",";
}
return 0;
}
