割点

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<algorithm>
#include<ctime>
using namespace std;
const int N=1000005;
int t,cnt,head[N],son[N],dfn[N],low[N],n,ans,m,root;
bool is_ok[N];
struct Node{
    int u,v,next;
}edge[N];
void push(int u,int v){
    ++cnt;
    edge[cnt].u=u;
    edge[cnt].v=v;
    edge[cnt].next=head[u];
    head[u]=cnt;
}
void tarjan(int v,int u){
    low[v]=dfn[v]=++t;
    for(int i=head[v];i!=-1;i=edge[i].next){
        ++son[v];
        int v1=edge[i].v;
        if(dfn[v1]==-1){
            tarjan(v1,v);
            low[v]=min(low[v],low[v1]);
            if(v==root&&son[v]>=2){
                is_ok[v]=true;
            }
            else if(v!=root&&low[v1]>=dfn[v]){
                is_ok[v]=true;
            }
        }
        else if(v1!=u){
            low[v]=min(low[v],dfn[v1]);
        }
    }
}
int main(){
    memset(head,-1,sizeof(head));
    memset(dfn,-1,sizeof(dfn));
    memset(is_ok,false,sizeof(is_ok));
    int u,v;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++){
        scanf("%d%d",&u,&v);
        push(u,v);
        push(v,u);
    }
    root=u;
    tarjan(u,0);
    for(int i=1;i<=n;i++){
        if(is_ok[i]){
            ++ans;
        }
    }
    printf("%d\n",ans);
    for(int i=1;i<=n;i++){
        if(is_ok[i]){
            printf("%d ",i);
        }
    }
    return 0;
}