Codeforces Round 918 (Div. 4) 1915F. Greetings Solution

 

Problem Link :   https://codeforces.com/contest/1915/problem/F

Solution in C++:

1. /// Author : AH_Tonmoy
2. #include<bits/stdc++.h>
3. using namespace std;
4. using ll = long long ;
5. #include<ext/pb_ds/assoc_container.hpp>
6. #include<ext/pb_ds/tree_policy.hpp>
7. using namespace __gnu_pbds;
8. typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
9. int32_t main() {
10. ios_base::sync_with_stdio(0);
11. cin.tie(0);
12. int t ;
13. cin >> t ;
14. while(t--){
15. int n ; cin >> n ;
16. vector<pair<int,int>>v;
17. pbds s ;
18. int x , y ;
19. for ( int i = 0 ; i < n; i++){
20. cin >> x >> y ;
21. s.insert(y) ;
22. v.push_back({x,y}) ;
23. }
24. sort(v.begin(),v.end()) ;
25. long long ans = 0 ;
26. for(auto u : v){
27. int x = u.second;
28. int y = s.order_of_key(x);
29. ans += y;
30. s.erase(x);
31. }
32. cout << ans << '\n';
33. }
34. return 0 ;
35. }