Submission #1080084

#	Time	Username	Problem	Language	Result	Execution time	Memory
1080084		jk_	Pipes (CEOI15_pipes)	C++14	40 / 100	773 ms	42836 KiB

pipes

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

struct ufind {
  vector<int> c;
  ufind(int n) : c(n) { iota(c.begin(), c.end(), 0); }
  int find(int k) { return c[k] == k ? k : (c[k] = find(c[k])); }
  void unite(int a, int b) { c[find(a)] = find(b); }
};

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);

  int n, m; cin >> n >> m;
  vector<pair<int, int>> edges;
  {
    array<ufind, 2> msts{{ufind(n), ufind(n)}};

    for (int i = 0; i < m; ++i) {
      int a, b; cin >> a >> b; --a; --b;
      for (auto& mst : msts) {
        if (mst.find(a) != mst.find(b)) {
          mst.unite(a, b);
          edges.emplace_back(a, b);
          break;
        }
      }
    }
  }

  vector<vector<int>> g(n);
  for (auto [a, b] : edges) {
    g[a].push_back(b);
    g[b].push_back(a);
  }
  edges.clear();

  vector<bool> visited(n);
  vector<int> pre(n, -1), low(n, -1);
  int timer=0;

  auto dfs = [&](auto&& self, int v, int p = -1) -> void {
    visited[v] = true;
    pre[v] = low[v] = timer++;
    bool used_p = false;
    for (auto w : g[v]) {
      if (w == p && !used_p) { used_p = true; continue; }
      if (visited[w]) {
        low[v] = min(low[v], pre[w]);
      } else {
        self(self, w, v);
        low[v] = min(low[v], low[w]);
        if (low[w] > pre[v]) {
          cout << v+1 << ' ' << w+1 << '\n';
        }
      }
    }
  };
  for (int i = 0; i < n; ++i)
    if (!visited[i])
      dfs(dfs, i);
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:33:13: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   33 |   for (auto [a, b] : edges) {
      |             ^

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10