Submission #321360

#	Time	Username	Problem	Language	Result	Execution time	Memory
321360		kshitij_sodani	Pastiri (COI20_pastiri)	C++14	0 / 100	1102 ms	55856 KiB

pastiri

//#pragma GCC optimize("Ofast,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
typedef long long llo;
#define mp make_pair
#define pb push_back
#define a first 
#define b second
//#define endl '\n'

int n,k;
vector<int> adj[500001];
vector<int> ans;
int lev[500001];
int par[500001][20];
int vis[500001];
int vis2[500001];
int mi[500001];
void dfs(int no,int par2=-1,int levv=0){
	lev[no]=levv;
	par[no][0]=par2;
	for(auto j:adj[no]){
		if(j!=par2){
			dfs(j,no,levv+1);
		}
	}
}
int cot=-1;
int dist[2001][2001];
void dfs2(int no,int par2=-1,int levv=0){
	if(vis2[no]){
		mi[cot]=min(mi[cot],levv);
	}
	dist[cot][no]=levv;
	for(auto j:adj[no]){
		if(j!=par2){
			dfs2(j,no,levv+1);
		}
	}
}
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cin>>n>>k;
	for(int i=0;i<n-1;i++){
		int aa,bb;
		cin>>aa>>bb;
		aa--;
		bb--;
		adj[aa].pb(bb);
		adj[bb].pb(aa);
	}
	vector<int> ss(k);
	for(int i=0;i<k;i++){
		cin>>ss[i];
		ss[i]--;
		vis2[ss[i]]=1;
	}
	for(int i=0;i<n;i++){
		mi[i]=n;
	}
	queue<pair<int,int>> mm;
	for(auto j:ss){
		mi[j]=0;
		mm.push({0,j});
	}
	while(mm.size()){
		pair<int,int> no=mm.front();
		mm.pop();
		for(auto j:adj[no.b]){
			if(mi[j]==n){
				mi[j]=no.a+1;
				mm.push({mi[j],j});
			}
		}
	}

	for(int i=0;i<n;i++){
		cot=i;
		dfs2(i);

	}
	for(int j=1;j<20;j++){
		for(int i=0;i<n;i++){
			if(par[i][j-1]==-1){
				par[i][j]=-1;
			}
			else{
				par[i][j]=par[par[i][j-1]][j-1];
			}
		}
	}

	dfs(0);
	vector<pair<int,int>> tt;
	for(auto j:ss){
		tt.pb({lev[j],j});
	}
	sort(tt.begin(),tt.end());
	while(tt.size()){
		if(vis[tt.back().b]){
			tt.pop_back();
			continue;
		}
		int x=tt.back().b;

		int cur=x;
		int co=0;
		for(int j=19;j>=0;j--){
			if(par[cur][j]==-1){
				continue;
			}
			if((1<<j)+co==mi[par[cur][j]]){
				cur=par[cur][j];
			}
		}
		/*int pp=x;
		int co=1;
		while(cur!=-1){
			if(co==mi[cur]){
				pp=cur;
				cur=par[cur];
				co++;
				continue;
			}
			break;
		}*/
		for(int i=0;i<k;i++){
			if(dist[cur][ss[i]]==mi[cur]){
				vis[ss[i]]=1;
			}
		}
		ans.pb(cur);
		tt.pop_back();
	}
	cout<<ans.size()<<endl;
	for(auto j:ans){
		cout<<j+1<<" ";
	}
	cout<<endl;











 
 
	return 0;
}

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