Submission #878427

#	Time	Username	Problem	Language	Result	Execution time	Memory
878427		Uladzimir_Rickey	Railway (BOI17_railway)	C++17	100 / 100	195 ms	45264 KiB

railway

#include <bits/stdc++.h>
#define pii pair<int, int>
#define pb push_back
#define F first
#define S second
using namespace std;
const int N = 1e5 + 10, LG = 20;
int h[N], par[N][LG], k;
vector<pii> adj[N];
vector<int> del[N], ans;
set<int> s[N];
 
void dd (int v, int p = -1) {
  par[v][0] = p;
  if (p != -1) h[v] = h[p] + 1;
  for (int i = 1; i < LG; i++) 
    if (par[v][i - 1] != -1) 
      par[v][i] = par[par[v][i - 1]][i - 1];
  for (auto u: adj[v])
    if (p != u.F) 
      dd(u.F, v);
}
 
int lca (int u, int v) {
  if (h[u] < h[v]) swap(u, v);
  for (int i = LG - 1; i >= 0; i--)
    if (par[u][i] != -1 && h[par[u][i]] >= h[v])
      u = par[u][i];
  if (u == v) return u;
  for (int i = LG - 1; i >= 0; i--)
    if (par[u][i] != par[v][i])
      u = par[u][i], v = par[v][i];
  return par[u][0];
}
 
void dfs (int v, int p = -1) {
  for (auto u: adj[v]) {
    if (u.F != p) {
      dfs(u.F, v);
      if (s[u.F].size() >= k) {
        ans.pb(u.S);
      }
      if (s[v].size() < s[u.F].size()) s[v].swap(s[u.F]);
      for (auto uu: s[u.F]) s[v].insert(uu);
      s[u.F].clear();
      for (auto u: del[v]) s[v].erase(u);
    }
  }
}
 
int main() {
  ios::sync_with_stdio(false);cin.tie(0);
  int n, m;
  cin >> n >> m >> k;
  memset(par, -1, sizeof par);
  for (int i = 1; i < n; i++) {
    int u, v;
    cin >> u >> v;
    adj[u].pb({v, i});
    adj[v].pb({u, i});
  }
  dd(1);
  for (int i = 1; i <= m; i++) {
    int x;
    cin >> x;
    vector<int> d(x);
    for (int j = 0; j < x; j++)
      cin >> d[j];
    for (auto u: d) s[u].insert(i);
    int l = lca(d[0], d[1]);
    for (int i = 2; i < x; i++)
      l = lca(l, d[i]);
    del[l].pb(i);
  }
  dfs(1);
  cout << ans.size() << '\n';
  sort(ans.begin(), ans.end());
  for (auto u: ans) cout << u << ' ';
  cout << '\n';
  return 0;
}

Compilation message (stderr)

railway.cpp: In function 'void dfs(int, int)':
railway.cpp:40:25: warning: comparison of integer expressions of different signedness: 'std::set<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   40 |       if (s[u.F].size() >= k) {
      |           ~~~~~~~~~~~~~~^~~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 16 / 16
• Subtask 6: 25 / 25