Submission #1127059

#	Time	Username	Problem	Language	Result	Execution time	Memory
1127059		JelalTkm	Network (BOI15_net)	C++20	0 / 100	0 ms	328 KiB

net

#include <bits/stdc++.h>
#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")

using namespace std;

#define int long long int

const int N = 2e1 + 10;
const int md = 1e9 + 7;
const int INF = 1e9;

int32_t main(int32_t argc, char *argv[]) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  
  int T = 1;
  // cin >> T;
  while (T--) {
    int n;
    cin >> n;
    vector<vector<int>> g(n + 1, vector<int> ());
    vector<int> p(n + 1);
    for (int i = 0; i < n - 1; i++) {
      int u, v;
      cin >> u >> v;
      g[u].push_back(v);
      g[v].push_back(u);
    }

    vector<int> a;
    for (int i = 1; i <= n; i++)
      if ((int) g[i].size() == 1)
        a.push_back(i);

    cout << (((int) a.size() + 1) >> 1) << '\n';

    vector<int> q;
    int y = -1;
    for (int i = 0; i < (int) a.size(); i++) {
      if (a[i] == -1)
        continue;
      bool ok = 0;
      for (int j = i + 1; j < (int) a.size(); j++) {
        if (a[j] == -1)
          continue;
        if (g[a[i]][0] == g[a[j]][0])
          continue;
        cout << a[i] << " " << a[j] << '\n';
        y = a[i];
        a[i] = a[j] = -1;
        ok = 1;
        break;
      }
      if (!ok)
        q.push_back(a[i]);
    }

    for (int i = 0; i < (int) q.size(); i += 2) {
      if (i + 1 < (int) q.size())
        cout << q[i] << " " << q[i + 1] << '\n';
      else cout << q[i] << " " << (y != -1 ? y : q[i - 1]) << '\n';
    }
  }
 
  return 0;
}

• Subtask 1: 0 / 18
• Subtask 2: 0 / 45
• Subtask 3: 0 / 37