Submission #679583

#	Time	Username	Problem	Language	Result	Execution time	Memory
679583		peijar	Network (BOI15_net)	C++17	100 / 100	419 ms	46660 KiB

net

#include <bits/stdc++.h>
#define int long long
using namespace std;

namespace std {
template <typename T> ostream &operator<<(ostream &out, const vector<T> &vec) {
  out << "[";
  for (int i = 0; i < (int)vec.size(); ++i) {
    out << vec[i];
    if (i + 1 < (int)vec.size())
      out << ", ";
  }
  return out << "]";
}
} // namespace std

void dbg_out() { cout << endl; }
template <typename Head, typename... Tail> void dbg_out(Head H, Tail... T) {
  cout << ' ' << H;
  dbg_out(T...);
}

#ifdef DEBUG
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

signed main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(0);

  int nbSommet;
  cin >> nbSommet;
  vector<vector<int>> adj(nbSommet);
  for (int i = 1; i < nbSommet; ++i) {
    int u, v;
    cin >> u >> v;
    --u, --v;
    adj[u].push_back(v);
    adj[v].push_back(u);
  }

  vector<int> feuilles;

  auto DFS = [&](auto dfs, int u, int p) -> void {
    if (adj[u].size() == 1)
      feuilles.push_back(u);
    for (int v : adj[u])
      if (v != p)
        dfs(dfs, v, u);
  };

  for (int u = 0; u < nbSommet; ++u)
    if (adj[u].size() > 1) {
      DFS(DFS, u, u);
      break;
    }

  int nbFeuilles = feuilles.size();
  int delta = (nbFeuilles + 1) / 2;
  cout << (nbFeuilles + 1) / 2 << endl;
  for (int i = 0; i < (nbFeuilles + 1) / 2; ++i)
    cout << 1 + feuilles[i] << ' ' << feuilles[(i + delta) % nbFeuilles] + 1
         << '\n';
}

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