1001 A+B Format (20point(s)) Easy only once

 1 #include<iostream>
 2 #include<stdlib.h>
 3 #include<stdio.h>
 4 #include<vector> 
 5 #include<string>
 6 #include<math.h>
 7 #include<algorithm>
 8 using namespace std;
 9 using std::vector;
10 int main() {
11     int a, b;
12     cin >> a >> b;
13     int c = a + b;
14     string s;
15     if (c < 0) {
16         cout << ‘-‘;
17     }
18     c = abs(c);
19     if(c == 0) {
20         cout << 0 << endl;
21         system("pause");
22         return 0;
23     }
24     int index = 0;
25     while (c != 0) {
26         index++;
27         s.push_back(c % 10+‘0‘);
28         c = c / 10;
29         if (index % 3 == 0)
30             s.push_back(‘,‘);
31     }
32     if (*(s.end() - 1 )== ‘,‘)
33         s.pop_back();
34     reverse(s.begin(), s.end());
35     cout << s << endl;
36     system("pause");
37     return 0;
38 }