Submission #1155732

#	Time	Username	Problem	Language	Result	Execution time	Memory
1155732		fryingduc	Mergers (JOI19_mergers)	C++20	100 / 100	470 ms	83732 KiB

mergers

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

#ifdef duc_debug
#include "bits/debug.h"
#else
#define debug(...)
#endif

const int maxn = 5e5 + 5;
int n, s[maxn], k;
vector<int> g[maxn];
vector<int> grp[maxn];
int lab[maxn], par[maxn], h[maxn];
int deg[maxn];

int find(int u) {
  return lab[u] < 0 ? u : lab[u] = find(lab[u]);
}

void join(int u, int v) {
  u = find(u), v = find(v);
  if (u == v) return;
//  if (lab[u] > lab[v]) swap(u, v);
  lab[u] += lab[v];
  lab[v] = u;
}

void pre_dfs(int u, int prev) {
  for (auto v:g[u]) {
    if (v == prev) continue;
    par[v] = u;
    h[v] = h[u] + 1;
    pre_dfs(v, u);
  }
}

void solve() {
  cin >> n >> k;
  for (int i = 1; i < n; ++i) {
    int u, v; cin >> u >> v;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  for (int i = 1; i <= n; ++i) {
    cin >> s[i];
    grp[s[i]].push_back(i);
    lab[i] = -1;
  }
  par[1] = 1;
  pre_dfs(1, 0);
  for (int i = 1; i <= k; ++i) {
    if (grp[i].empty()) continue;
    for (int j = 1; j < (int)grp[i].size(); ++j) {
      int u = grp[i][j], v = grp[i][j - 1];
      u = find(u), v = find(v);
      while (u != v) {
        if (h[u] > h[v]) swap(u, v);
        join(u, v); 
        v = find(par[v]);
        u = find(u);
      }
    }
  }
  for (int i = 1; i <= n; ++i) {
    int u = find(i);
    for (auto v:g[i]) {
      v = find(v);
      if (u != v) {
        ++deg[u];
      }
    }
  }
  int cnt = 0;
  for (int i = 1; i <= n; ++i) {
    cnt += (deg[i] == 1);
  }
  cout << (cnt + 1) / 2;
}

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

  solve();

  return 0;
}

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