Luogu 3388（割点）

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注意：统计割点个数一定要注意算重！！！有多个儿子使当前点成为割点时计数器也只能加一次！！！

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>using namespace std;const int N=1e5+4;int n,m,dfn[N],low[N],tim=0,cut=0;int head[N],etot=0;struct EDGE {int v,nxt;}e[N<<1];bool iscut[N];inline int read() {int x=0;char c=getchar();while (c<'0'||c>'9') c=getchar();while (c>='0'&&c<='9') x=(x<<3)+(x<<1)+c-'0',c=getchar();return x;}inline void adde(int u,int v) {e[etot].nxt=head[u],e[etot].v=v,head[u]=etot++;e[etot].nxt=head[v],e[etot].v=u,head[v]=etot++;}void dfs(int p,int fa) {low[p]=dfn[p]=++tim;int ch=0;for (int i=head[p];~i;i=e[i].nxt) {int v=e[i].v;if (!dfn[v]) {++ch;dfs(v,p);low[p]=min(low[p],low[v]);if (low[v]>=dfn[p]) cut+=!iscut[p],iscut[p]=true;}else if (dfn[v]<dfn[p]&&v^fa) low[p]=min(low[p],dfn[v]);}if (fa==-1&&ch==1) iscut[p]=false,--cut;}int main() {//freopen("P3388.in","r",stdin);memset(dfn,0,sizeof(dfn));memset(head,-1,sizeof(head));memset(iscut,false,sizeof(iscut));n=read(),m=read();for (register int i=0;i<m;++i) {int u=read(),v=read();adde(u,v);}for (register int i=1;i<=n;++i)if (!dfn[i]) dfs(i,-1);printf("%d\n",cut);for (register int i=1;i<=n;++i)if (iscut[i]) printf("%d ",i);return 0;}