AC代码：

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 5;
int n, m, dfn[maxn], low[maxn], idx, rt;
bool cut[maxn];
vector<int> g[maxn];

void tarjan(int u, int p) {
	dfn[u] = low[u] = ++idx;
	int son_cnt = 0;
	for (auto v : g[u]) {
		if (v == p) continue;
		if (!dfn[v]) {
			tarjan(v, u);
			son_cnt++;
			low[u] = min(low[u], low[v]);
			if (u != rt && low[v] >= dfn[u])
				cut[u] = true;
		}
		else
			low[u] = min(low[u], dfn[v]);
	}
	if (u == rt && son_cnt > 1)
		cut[u] = true;
}

int main() {
	scanf("%d%d", &n, &m);
	while (m--) {
		int u, v;
		scanf("%d%d", &u, &v);
		g[u].push_back(v);
		g[v].push_back(u);
	}
	for (int i = 1; i <= n; i++)
		if (!dfn[i])
			rt = i,
			tarjan(i, -1);
	int cnt = 0;
	for (int i = 1; i <= n; i++)
		cnt += cut[i];
	printf("%d\n", cnt);
	for (int i = 1; i <= n; i++)
		if (cut[i])
			printf("%d ", i);
	return 0;
}

代码有问题：

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 5;
int n, m, dfn[maxn], low[maxn], idx, rt;
bool cut[maxn];
vector<int> g[maxn];

void tarjan(int u, int p) {
	dfn[u] = low[u] = ++idx;
	int son_cnt = 0;
	for (auto v : g[u]) {
		if (v == p) continue;
		if (!dfn[v]) {
			tarjan(v, u);
			son_cnt++;
			low[u] = min(low[u], low[v]);
		}
		else 
			low[u] = min(low[u], dfn[v]);
	}
	if (dfn[u] == low[u]) {
		if (u != rt && son_cnt > 0 || u == rt && son_cnt > 1)
			cut[u] = true;
	}
}

int main() {
	scanf("%d%d", &n, &m);
	while (m--) {
		int u, v;
		scanf("%d%d", &u, &v);
		g[u].push_back(v);
		g[v].push_back(u);
	}
	for (int i = 1; i <= n; i++)
		if (!dfn[i])
			rt = i,
			tarjan(i, -1);
	int cnt = 0;
	for (int i = 1; i <= n; i++)
		cnt += cut[i];
	printf("%d\n", cnt);
	for (int i = 1; i <= n; i++)
		if (cut[i])
			printf("%d ", i);
	return 0;
}