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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.     ios::sync_with_stdio(false);
  6.     cin.tie(nullptr);
  7.  
  8.     int t;
  9.     cin >> t;
  10.  
  11.     while (t--) {
  12.         int n;
  13.         cin >> n;
  14.  
  15.         vector<vector<int>> edges(n + 1);
  16.         for (int i = 0; i < n - 1; i++) {
  17.             int u, v;
  18.             cin >> u >> v;
  19.             edges[u].push_back(v);
  20.             edges[v].push_back(u);
  21.         }
  22.  
  23.         vector<int> ks(n + 1);
  24.         long long ans = 0;
  25.  
  26.         for (int x = 1; x <= n; x++) {
  27.             if (edges[x].size() == 1) {
  28.                 ans += n - 2;
  29.                 int y = edges[x][0];
  30.                 ks[y]++;
  31.             }
  32.         }
  33.  
  34.         for (int x = 0; x <= n; x++) {
  35.             ans -= 1LL * ks[x] * (ks[x] - 1) / 2;
  36.             if (edges[x].size() == 2 && ks[x] == 0) ans++;
  37.         }
  38.  
  39.         cout << 1LL * n * (n - 1) * (n - 2) / 6 - ans << '\n';
  40.     }
  41. }
  42.  
Success #stdin #stdout 0s 5324KB
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https://ideone.com/ADckkq
language:
C++ (gcc 8.3)
created:
2 days ago
visibility:
public

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