luogu3388 【模板】割点（割顶）

模板题

#include <iostream>
#include <cstdio>
using namespace std;
struct Edge{
	int too, nxt;
}edge[200005];
int n, m, dfn[100005], loo[100005], ind, uu, vv, cnt, hea[100005];
bool isa[100005];
void add_edge(int fro, int too){
	edge[++cnt].nxt = hea[fro];
	edge[cnt].too = too;
	hea[fro] = cnt;
}
void tarjan(int u, int f){
	dfn[u] = loo[u] = ++ind;
	int cd=0;
	for(int i=hea[u]; i; i=edge[i].nxt){
		int t=edge[i].too;
		if(!dfn[t]){
			cd++;
			tarjan(t, u);
			loo[u] = min(loo[u], loo[t]);
			if(f!=-233 && loo[t]>=dfn[u])	isa[u] = true;
		}
		loo[u] = min(loo[u], dfn[t]);
	}
	if(f<0 && cd>=2)	isa[u] = true;
}
int main(){
	cin>>n>>m;
	for(int i=1; i<=m; i++){
		scanf("%d %d", &uu, &vv);
		add_edge(uu, vv);
		add_edge(vv, uu);
	}
	for(int i=1; i<=n; i++)
		if(!dfn[i])
			tarjan(i, -233);
	int ans=0;
	for(int i=1; i<=n; i++)
		if(isa[i])
			ans++;
	cout<<ans<<endl;
	for(int i=1; i<=n; i++)
		if(isa[i])
			printf("%d ", i);
	return 0;
}