bzoj4579[Usaco2016 Open]Closing the Farm--by lethalboy

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<string>
#define N 200020
#include<vector>
using namespace std;
int read()
{
int x=0,f=1;char ch;
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;
}
int n,m;
bool vis
,ok
;
vector<int>G
;
int a
,f
;
int find(int x){return x==f[x]?x:f[x]=find(f[x]);}
int main()
{
n=read(),m=read();
for(int i=1,a,b;i<=m;i++)
{
scanf("%d%d",&a,&b);
G[a].push_back(b);
G[b].push_back(a);
}
for(int i=1;i<=n;i++)
scanf("%d",&a[i]),f[i]=i;
int cnt=0;
for(int i=n;i;i--)
{
int u=a[i];
cnt++;vis[u]=1;
for(int j=0;j<G[u].size();j++)
{
int v=G[u][j];
if(!vis[v])continue;
int fa=find(u),fb=find(v);
if(fa!=fb)
{
if(fa>fb)swap(fa,fb);
f[fb]=fa;
cnt--;
}
}
if(cnt==1)ok[i]=1;
}
for(int i=1;i<=n;i++)
if(ok[i])printf("YES\n");
else printf("NO\n");
}</span><span style="font-size: 24px;">
</span>