正题

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题目大意

求所有割点

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解题思路

跑$tarjan$，然后判断$df{n}_x\le lo{w}_y$

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$code$

#include<cstdio>
#include<algorithm>
#define N 20100
#define M 100100
using namespace std;
struct node{int to,next;
}a[M*2];
int n,m,tot,dfn[N],low[N],ls[N],cnt,z,root;
bool mark[N],v[N];
void addl(int x,int y)
{a[++tot].to=y;a[tot].next=ls[x];ls[x]=tot;
}
void tarjan(int x)
{dfn[x]=low[x]=++cnt;int flag=0;for(int i=ls[x];i;i=a[i].next){int y=a[i].to;v[y]=0;if(!dfn[y]){tarjan(y);low[x]=min(low[x],low[y]);if(dfn[x]<=low[y]){flag++;if((x!=root||flag>1)&&!mark[x])mark[x]=1,z++;}}else low[x]=min(low[x],dfn[y]);}
}
int main()
{scanf("%d%d",&n,&m);for(int i=1;i<=m;i++){int x,y;scanf("%d%d",&x,&y);if(x==y) continue;addl(x,y);addl(y,x);}for(int i=1;i<=n;i++)if(!dfn[i]) root=i,tarjan(i);printf("%d\n",z);for(int i=1;i<=n;i++)if(mark[i]) printf("%d ",i);
}