tarjan 强联通分量和割点

#include<cstdio> 
#include<cstring>
#include<cmath>
#include<ctime>
#include<iostream>
#include<algorithm>
#include<queue>
#include<stack>
#include<set>
#define esp (1e-6)
#define inf (0x3f3f3f3f)
#define l(a) ((a)<<1)
#define r(a) ((a)<<1|1)
#define b(a) (1<<(a))
#define rep(i,a,b) for(int i=a;i<=(b);i++)
#define clr(a) memset(a,0,sizeof(a))
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
int readint(){
    int t=0,f=1;char c=getchar();
    while(!isdigit(c)){
        if(c=='-') f=-1;
        c=getchar();
    }
    while(isdigit(c)){
        t=(t<<3)+(t<<1)+c-'0';
        c=getchar();
    }
    return t*f;
}
const int maxn=100009,maxm=200009;
struct edge{
    int v;
    edge*next;
}e[maxm],*pt=e,*fir[maxn];
int n,m,ans,dfstime,scccnt,size[maxn],pre[maxn],low[maxn],scc[maxn];
bool p[maxn];
void add(int u,int v){
    pt->v=v;pt->next=fir[u];
    fir[u]=pt++;
}
void addedge(int u,int v){
    add(u,v);add(v,u);
}
stack<int>S;
void dfs(int x,int f){
    int son=0;
    pre[x]=low[x]=++dfstime;S.push(x);
    for(edge*e=fir[x];e;e=e->next) if(e->v!=f){
        if(!pre[e->v]){
            son++;dfs(e->v,x);
            low[x]=min(low[x],low[e->v]);
            if(f!=-1&&low[e->v]>=pre[x]) p[x]=1;
        }else if(!scc[e->v]) low[x]=min(low[x],pre[e->v]);
    }
    if(f==-1&&son>1) if(!p[x]) p[x]=1;
    if(pre[x]==low[x]){
        int t=-1;++scccnt;
        while(t!=x){
            t=S.top();S.pop();
            scc[t]=scccnt;size[scccnt]++;
        }
    }
}
void tarjan(){
    rep(i,1,n) if(!scc[i]) dfs(i,-1);
    rep(i,1,n) if(p[i]) ans++;
    cout<<ans<<endl;
    rep(i,1,n) if(p[i]){
        ans--;printf("%d",i);
        putchar(ans?' ':'
');
    }
}
int main(){
    //freopen("#input.txt","r",stdin);
    //freopen("#output.txt","w",stdout);
    n=readint();m=readint();
    rep(i,1,m){
        int U=readint(),V=readint();
        addedge(U,V);
    }
    tarjan();
    //fclose(stdin);
    //fclose(stdout);
    return 0;
}