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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. using ll = long long;
  4.  
  5. int main() {
  6.     ios::sync_with_stdio(false);
  7.     cin.tie(nullptr);
  8.  
  9.     int n;
  10.     cin >> n;
  11.     vector<ll> u(n + 1);
  12.     for (int i = 1; i <= n; i++) cin >> u[i];
  13.  
  14.     sort(u.begin() + 1, u.end());
  15.  
  16.     ll ans = 0;
  17.     for (int k = 3; k <= n; k++) {
  18.         int i = 1, j = k - 1;
  19.         while (i < j) {
  20.             if (u[i] + u[j] > u[k]) {
  21.                 ans += (j - i);
  22.                 j--;
  23.             } else {
  24.                 i++;
  25.             }
  26.         }
  27.     }
  28.  
  29.     cout << ans;
  30.     return 0;
  31. }
Success #stdin #stdout 0.01s 5316KB
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https://ideone.com/EDIrdA
language:
C++ (gcc 8.3)
created:
3 days ago
visibility:
public

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