Submission #993448

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Source Code Expand

#include <bits/stdc++.h>
#define FOR(i,a,b) for(ut i=(a);i<(ut)(b);i++)
#define REP(i,b) FOR(i,0,b)
#define ALL(c) c.begin(),c.end()
#define PB push_back
#define cat //cout << __LINE__ << endl;
using namespace std;
typedef long long LL;
typedef double ld;
typedef LL ut;
typedef vector<ut> VI;
typedef pair<ut,ut> pr;
typedef pair<ut,pr> ppr;
typedef vector<pr> Vpr;
typedef vector<ppr> Vppr;
typedef priority_queue<pr,Vpr,greater<pr> > PQ;
using namespace std;
const int SIZE=5*1e5;
const LL INF=1LL<<58;
const LL p=1e9+7;
class UnionFind{
 
	vector<int> unions,talls,sents,dists,sizes;
	int size;
public:
	UnionFind(){}
	UnionFind(int size):size(size){
		init();
	}
	void init(){
	 	unions=vector<int>(size);
	 	talls=vector<int>(size);
	 	sents=vector<int>(size);
	 	dists=vector<int>(size);
	 	sizes=vector<int>(size);
		FOR(i,0,size){
			unions[i]=i;
			sents[i]=0;
			sizes[i]=1;
//			ns[i].PB(pr(0,1));
			talls[i]=1;
		}
	}
	int find(int x,int t=0){
		if(unions[x]==x || sents[x]>t) return x;
		return find(unions[x],t);
 
	}
	int minisize(int x){
		if(x==unions[x]) return sizes[x];
		return minisize(find(x));
	}
	bool isFriend(int a,int b,int t=0){
		return find(a,t)==find(b,t);	
	}
	void unite(int a,int b,int t=0){
		if(isFriend(a,b,t)) return;
		a=find(a,t);
		b=find(b,t);
		if(talls[a]<talls[b]) unite(b,a,t);
		else{
 			sizes[a]+=sizes[b];
			sents[b]=t;
			talls[a]=max(talls[a],talls[b]+1);
			unions[b]=a;
			dists[b]=1;
//			ns[a].PB(pr(t,ns[b].back().second+ns[a].back().second));
		}
	}
};
UnionFind uf=UnionFind(1e5+5);
int L[SIZE];
bool userable[SIZE];
bool solve(){
	int N,K,M;
	cin.tie(0);
	cin >> N >> M;
	REP(i,N){
		cin >> K;
		REP(i,K){
			cin >> L[i];
			userable[L[i]]=true;
			uf.unite(L[0],L[i]);
		}
	}
	int roots=0;
	FOR(i,1,M+1){
		if(userable[i]&&uf.find(i)==i) roots++;
	}
	return roots==1;
}
int main(){
	if(solve()) cout <<"YES" << endl;
	else cout << "NO" << endl;
	return 0;
}

Submission Info

Judge Result