Submission #220086

#	Time	Username	Problem	Language	Result	Execution time	Memory
220086		rama_pang	Mergers (JOI19_mergers)	C++14	100 / 100	757 ms	91896 KiB

mergers

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

class DisjointSet {
 private:
  int n;
  vector<int> p;

 public:
  DisjointSet(int n) : n(n) {
    p.resize(n);
    iota(begin(p), end(p), 0);
  }

  int Find(int x) {
    return p[x] == x ? x : p[x] = Find(p[x]);
  }

  bool Union(int x, int y) {
    x = Find(x);
    y = Find(y);
    if (x == y) return false;
    p[y] = x;
    return true;
  }

  bool IsRoot(int x) {
    return p[x] == x;
  }
};

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0), cout.tie(0);

  int N, K;
  cin >> N >> K;

  vector<vector<int>> adj(N + 1);
  for (int i = 0; i < N - 1; i++) {
    int u, v;
    cin >> u >> v;
    adj[u].emplace_back(v);
    adj[v].emplace_back(u);
  }

  vector<vector<int>> colorList(K);
  for (int i = 1; i <= N; i++) {
    int c;
    cin >> c;
    colorList[--c].emplace_back(i);
  }

  vector<int> par(N + 1);
  vector<int> depth(N + 1);
  DisjointSet group(N + 1);

  function<void(int)> Dfs = [&](int n) {
    for (auto i : adj[n]) if (i != par[n]) {
      depth[i] = depth[n] + 1;
      par[i] = n;
      Dfs(i);
    }
  };

  auto Unite = [&](int a, int b) {
    a = group.Find(a);
    b = group.Find(b);
    while (a != b) {
      if (depth[a] > depth[b]) swap(a, b);
      group.Union(par[b], b);
      b = group.Find(b);
    }
  };

  depth[1] = 1;
  par[1] = 0;
  Dfs(1);

  for (int k = 0; k < K; k++) {
    for (int i = 1; i < (int) colorList[k].size(); i++) {
      Unite(colorList[k][0], colorList[k][i]);
    }
  }

  vector<int> degree(N + 1, 0);
  for (int i = 1; i <= N; i++) {
    for (auto j : adj[i]) {
      if (group.Find(i) != group.Find(j)) {
        degree[group.Find(i)]++;
      }
    }
  }

  int ans = 0;
  for (int i = 1; i <= N; i++) {
    if (group.IsRoot(i) && degree[i] == 1) {
      ans++;
    }
  }

  cout << ((ans + 1) / 2) << "\n";
  return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 24 / 24
• Subtask 3: 14 / 14
• Subtask 4: 22 / 22
• Subtask 5: 30 / 30