洛谷 P3388 【模板】割点

#include <algorithm>
#include <ctype.h>
#include <cstring>
#include <cstdio>
#define N 100005
using namespace std;
void read(int &x)
{
    x=0;char ch=getchar();
    while(!isdigit(ch)) ch=getchar();
    while(isdigit(ch))
    {
        x=x*10+ch-‘0‘;
        ch=getchar();
    }
}
bool vis[N],cutpoint[N],cutedge[N];
int ans[N],l,low[N],dfn[N],tim,n,m,cnt=-1,head[N];
struct node
{
    int next,to;
}edge[N<<1];
void add(int u,int v)
{
    ++cnt;
    edge[cnt].next=head[u];
    edge[cnt].to=v;
    head[u]=cnt;
}
int min(int a,int b){return a>b?b:a;} 
void tarjan(int x,int pre)
{
    low[x]=dfn[x]=++tim;
    vis[x]=1;
    int sum=0;
    bool flag=false;
    for(int i=head[x];i!=-1;i=edge[i].next)
    {
        if((i^1)!=pre)
         if(!vis[edge[i].to])
         {
             sum++;
            tarjan(edge[i].to,i);
            if(low[edge[i].to]>=dfn[x]) flag=true; 
            low[x]=min(low[x],low[edge[i].to]);
         }
         else low[x]=min(low[x],dfn[edge[i].to]);
    }
    if(pre==-1)
    {
        if(sum>1) cutpoint[x]=true;
    } 
    else
    {
        if(flag) cutpoint[x]=true;
    } 
}
int main()
{
    memset(head,-1,sizeof(head));
    read(n);read(m);
    for(int x,y;m--;)
    {
        read(x);read(y);
        add(x,y);
        add(y,x);
    }
    for(int i=1;i<=n;i++)
        if(!vis[i]) tarjan(i,-1);
    for(int i=1;i<=n;i++)
        if(cutpoint[i]) l++,ans[l]=i;
    printf("%d\n",l);
    for(int i=1;i<=l;i++) printf("%d ",ans[i]);
    return 0;
}