Submission #3556342

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Source Code Expand

#include<cstdio>
#include<iostream>
#include<cstring>
#define RG register
using namespace std;
const int N=1e5+10;
int n,lst[N],fa[N],m,k,cnt;
inline int read(){
	char ch=getchar(); int x=0, f=1;
	while(ch<'0' || ch>'9'){if(ch=='-') f=-1; ch=getchar();	}
	while(ch>='0' && ch<='9'){x=x*10+ch-'0'; ch=getchar();	}
	return x*f;}
inline int f(int son){return fa[son]==son ? son : f(fa[son]);}
int main()
{
	//freopen("Interpretation.in","r",stdin);
	//freopen(".out","w",stdout);
	n=read(); m=read();
	for(int i=1;i<=n;i++) fa[i]=i;
	for(int i=1;i<=n;i++)
	{
		k=read();
		for(int j=1,a;j<=k;j++)
		{
			a=read();
			if(!lst[a]) 
			{
				lst[a]=i;
				continue;
			}
			int fx=f(lst[a]), fy=f(i);
			if(fx!=fy) fa[fx]=fy;
			lst[a]=i;
		}
	}
	for(int i=1;i<=n;i++)
	{
		if(fa[i]==i) cnt++;
		if(cnt>=2) return printf("NO\n"), 0;
	}
	return printf("YES\n"), 0;
	//fclose(stdin); fclose(stdout);
	return 0;
}

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