Shared code

// Fixed https://codeforces.com/blog/entry/68138#comment-650743
#include <iostream>
#include <vector>
 
using namespace std;
 
const int MAX_N = 300005;
 
int bridgec;
vector<int> adj [MAX_N];
 
int lvl [MAX_N];
int dp [MAX_N];
 
vector<int> ans;
 
void visit (int vertex) {
	dp[vertex] = 0;
	vector<int> temp;
	int par = 0;
	int child = 0;
	for (int nxt : adj[vertex])
	{
		if (lvl[nxt] == 0)
		{	/* edge to child */
			child++;
			if (!temp.empty())
			{
				temp[temp.size() - 1] -= par;
				par = 0;
			}
			lvl[nxt] = lvl[vertex] + 1;
			visit(nxt);
			dp[vertex] += dp[nxt];
			temp.push_back(dp[nxt]);
		}
		else if (lvl[nxt] < lvl[vertex])
		{	/* edge upwards */
			dp[vertex]++;
		}
		else if (lvl[nxt] > lvl[vertex])
		{	/* edge downwards */
			dp[vertex]--;
			par++;
		}
 
	}
	/* the parent edge isn't a back-edge, subtract 1 to compensate */
	dp[vertex]--;
 
	//Special Cases
	if (child == 0)
		return;//leave node
	if (vertex == 1)
	{
		// root node
		if (child > 1)
		{
			// cout << "vertex " << vertex << endl;
			ans.push_back(vertex);
			bridgec++;
		}
		return;
	}
 
	//General Cases
	temp[temp.size() - 1] -= par;
	int flag = 0;
	for (int x : temp)
	{
		if (x > 0) continue;
		else {
			flag = 1;
		}
	}
	if (flag)
	{
		// cout << "vertex " << vertex << endl;
		ans.push_back(vertex);
		bridgec++;
	}
}
 
int main () {
	/* problem statement: given a connected graph. calculate the number of articulation points. */
	ios_base::sync_with_stdio(0); cin.tie(0);
	int vertexc, edgec;
	cin >> vertexc >> edgec;
 
	for (int i = 0; i < edgec; i++) {
		int u, v;
		cin >> u >> v;
 
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
 
	lvl[1] = 1;
	visit(1);
	// cout << bridgec << endl;
	cout << ans.size() << '\n';
	for (auto v : ans) cout << v << ' ';
}