Submission #1262217

#	Time	Username	Problem	Language	Result	Execution time	Memory
1262217		minhpk	Pastiri (COI20_pastiri)	C++20	0 / 100	393 ms	177532 KiB

pastiri

#include <bits/stdc++.h>
#define int long long
using namespace std;
int a,b;
vector <int> z[1000005];
vector <int> v;
int high[1000005];
int par[500005][25];
bool cmp(int a,int b){
     return high[a]>high[b];
}
void dfs(int i,int parent){
     for (auto p:z[i]){
          if (p==parent){
              continue;
          }
          high[p]=high[i]+1;
          par[p][0]=i;
          dfs(p,i);
     }
}
bool vis[1000005];
int cnt[1000005];
void bfs1(){
    queue<int> q;
    for (auto p:v){
         q.push(p);
         vis[p]=true;
         cnt[p]=0;
    }
    while (q.size()){
          int pos=q.front();
          q.pop();
          for (auto p:z[pos]){
               if (vis[p]){
                   continue;
               }
               vis[p]=true;
               cnt[p]=cnt[pos]+1;
               q.push(p);
          }
    }
}
vector <int> res;

int  jump(int x){
    for (int i=20;i>=0;i--){
         int nxt=par[x][i];
         if (cnt[nxt]==high[x]-high[nxt]){
             x=par[x][i];
         }
    }
    return x;
}
void bfs(int sta,int len){
     queue<pair<int,int>> q;
     q.push({sta,len});
     vis[sta]=true;
     while (q.size()){
          auto [pos,remain]=q.front();
          q.pop();
          if (remain==0){
             continue;
          }
          for (auto p:z[pos]){
               if (vis[p]){
                   continue;
               }
               vis[p]=true;
               q.push({p,remain-1});
          }
     }
}
signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> a >> b;
    for (int i=1;i<a;i++){
         int x,y;
         cin >> x >> y;
         z[x].push_back(y);
         z[y].push_back(x);
    }
    for (int i=1;i<=b;i++){
         int x;
         cin >> x;
         v.push_back(x);
    }
    high[0]=-1;
    par[1][0]=1;
    dfs(1,1);
    for (int j=1;j<=20;j++){
         for (int i=1;i<=a;i++){
              par[i][j]=par[par[i][j-1]][j-1];
         }
    }
    sort(v.begin(),v.end(),cmp);
    bfs1();
    memset(vis,false,sizeof vis);
    for (auto p:v){
         if (vis[p]){
             continue;
         }
         int nxt=jump(p);
         int len=high[p]-high[nxt];
         res.push_back(nxt);
         bfs(nxt,len);
    }
    cout << res.size() << "\n";
    for (auto p:res){
         cout << p << " ";
    }
    return 0;
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 18
• Subtask 3: 0 / 23
• Subtask 4: 0 / 51