Submission #1194668

#	Time	Username	Problem	Language	Result	Execution time	Memory
1194668		julia_08	Railway (BOI17_railway)	C++20	0 / 100	84 ms	26040 KiB

railway

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

const int MAXN = 1e5 + 10;

int marc[MAXN], deg[MAXN], nivel[MAXN];

int dp[20][MAXN];

vector<int> adj[MAXN];

int root = 1, nivel_root = 0;

set<int> active, leaf;

void dfs(int v, int p){

  for(auto u : adj[v]){
    if(u != p){
      nivel[u] = nivel[v] + 1;
      dp[0][u] = v;
      dfs(u, v);
    }
  }

}

int jump(int v){

  for(int k=19; k>=0; k--){
    if(nivel[dp[k][v]] < nivel_root) continue;
    if(!active.count(dp[k][v])) v = dp[k][v];
  }

  v = dp[0][v];
  return v;
}

int main(){
  cin.tie(0)->sync_with_stdio(0);

  int n, m, k; cin >> n >> m >> k;

  vector<pair<int, int>> edges;

  for(int i=1; i<n; i++){

    int a, b; cin >> a >> b;

    edges.push_back({a, b});

    adj[a].push_back(b);
    adj[b].push_back(a);

    deg[a] ++;
    deg[b] ++;

  }

  dp[0][root] = 1;
  dfs(root, root);

  for(int k=1; k<20; k++){
    for(int i=1; i<=n; i++){
      dp[k][i] = dp[k - 1][dp[k - 1][i]];
    }
  }

  for(int i=1; i<=n; i++){
    active.insert(i);
    if(deg[i] == 1) leaf.insert(i);
  }

  while(m--){

    int s; cin >> s;

    vector<int> vtx(s);

    for(int i=0; i<s; i++){
      cin >> vtx[i];
      if(!active.count(vtx[i])) vtx[i] = jump(vtx[i]);
      marc[vtx[i]] ++;
    }

    queue<int> q;

    for(auto x : leaf) q.push(x);

    while(!q.empty()){

      int v = q.front(); q.pop();

      if(marc[v]) continue;

      if(v == root) nivel_root ++;

      leaf.erase(v);
      active.erase(v);

      for(auto u : adj[v]){
        deg[u] --;
        if(deg[u] == 1){
          leaf.insert(u);
          q.push(u);
        }
      }

    }

    for(int i=0; i<s; i++) marc[vtx[i]] --;

  }

  cout << (int) active.size() - 1 << "\n";

  for(int i=0; i<(int) edges.size(); i++){
    if(active.count(edges[i].first) && active.count(edges[i].second)){
      cout << i + 1 << " ";
    }
  }

  cout << "\n";

  return 0;
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 0 / 7
• Subtask 4: 0 / 29
• Subtask 5: 0 / 16
• Subtask 6: 0 / 25