爆0求助

#include<iostream>
#include<cstdio>
#include<cstring>
#define rep(i,l,r)for(int i=l;i<=r;i++)
#define N 200010
#define M 100010
#define LL long long
using namespace std;
struct edge{
	int to,next;
}e[2*N];
int n,m;
int u,v,w;
int head[N],cnt;
int num[N],low[N],flag[N],idx;
LL ans=0;
void add_edge(int u,int v)
{
	e[++cnt].to=v;
	e[cnt].next=head[u];
	head[u]=cnt;
}
void dfs(int cur,int fa)
{
	int child=0;
	idx++;
	num[cur]=idx;
	low[cur]=idx;
	for(int i=head[cur];i!=-1;i=e[i].next)
	{
		int tmp=e[i].to;
		if(!num[tmp])
		{
			dfs(tmp,fa);
			low[cur]=min(low[cur],low[tmp]);
			if(cur!=fa&&low[tmp]>=num[cur])
				flag[cur]=1;
			if(cur==fa)
				child++;
		}
		low[cur]=min(low[cur],num[tmp]);
	}
	if(child>=2&&cnt==fa)
		flag[cnt]=1;
	return ;
}
int main()
{
	memset(head,-1,sizeof(head));
	memset(num,0,sizeof(num));
	memset(flag,0,sizeof(flag));
	scanf("%d%d",&n,&m);
	rep(i,1,m)
	{
		scanf("%d%d",&u,&v);
		add_edge(u,v);
		add_edge(v,u);
	}
	rep(i,1,n)
		if(num[i]==0)dfs(i,i);
	rep(i,1,n)
	{
		if(flag[i])ans++;
	}
	printf("%lld\n",ans);
	rep(i,1,n)
		if(flag[i])printf("%d ",i);
	printf("\n");
	return 0;
}