Luogu3388 cut point template

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

int head[1000005],low[1000005],dfn[1000005],cut[1000005],n,m,cnt,time;

struct edge{
    int v,next;
}e[1000005];

inline void add(int u,int v){
    e[++cnt].v=v;
    e[cnt].next=head[u];
    head[u]=cnt;
}

inline void tarjan(int u,int fa){
    low[u]=dfn[u]=++time;
    int child=0;
    for(int i=head[u];i!=-1;i=e[i].next){
        int v=e[i].v;
        if(!dfn[v]){
            tarjan(v,fa);
            low[u]=min(low[u],low[v]);
            if(low[v]>=dfn[u]&&u!=fa)cut[u]=1;
            if(u==fa)child++;
        }
        low[u]=min(low[u],dfn[v]);
    }
    if(child>=2&&u==fa)cut[u]=1;
}

int main(){
    memset(head,-1,sizeof(head));
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++){
        int x,y;
        scanf("%d%d",&x,&y);
        add(x,y);add(y,x);
    }
    for(int i=1;i<=n;i++)if(!dfn[i])tarjan(i,i);
    int ans=0;
    for(int i=1;i<=n;i++){
        if(cut[i])ans++;
    }
    printf("%d\n",ans);
    for(int i=1;i<=n;i++){
        if(cut[i])printf("%d ",i);
    }
}