Educational Codeforces Round 115 (Rated for Div. 2) 1598C. Delete Two Elements Solution

 Problem Link :   https://codeforces.com/contest/1598/problem/C

Solution in C++:

1. /// Author : AH_Tonmoy
2. #include <bits/stdc++.h>
3. using namespace std;
4. using ll = long long ;
5. int32_t main() {
6. ios_base::sync_with_stdio(0);
7. cin.tie(0);
8. int t;
9. cin >> t;
10. while (t--) {
11. int n ;
12. cin >> n ;
13. ll sum = 0 ;
14. int a[n+1] ;
15. for ( int i = 0 ; i < n ; i++) {
16. cin >> a[i] ;
17. sum += a[i] ;
18. }
19. ll ans = 0 ;
20. sum = sum * 2 ;
21. map<ll,int>mp ;
22. if (sum % n == 0){
23. int nav = sum/n ;
24. for ( int i = 0 ; i < n ; i++){
25. ans +=mp[nav- a[i]] ;
26. mp[a[i]]++ ;
27. }
28. }
29. cout << ans <<'\n' ;
30. }
31. return 0;
32. }