Tarjan-Hopcroft algorithm

void articulationDFS(int u, int &time)
{
    int childrenCount = 0;
    lowest[u] = discovery[u] = ++time;
    visited[u] = true;

    for(auto v : adj[u])
    {
        if(!visited[v])
        {
            childrenCount++;
            parent[v] = u;

            articulationDFS(v, time);

            lowest[u] = std::min(lowest[u], lowest[v]);

            if((parent[u] != -1 && lowest[v] >= discovery[u]) || (parent[u] == -1 && childrenCount > 1))
                AP[u] = true;
        }

        else if(v != parent[u])
            lowest[u] = std::min(lowest[u], discovery[v]);
    }
}

std::vector<int> findArticulationPoints()
{
    std::vector<int> articulationPoints;

    for(int i = 0; i < n; i++)
    {
        if(!visited[i])
        {
            int time = 0;
            articulationDFS(i, time);
        }
    }

    for(int i = 0; i < n; i++)
        if(AP[i])
            articulationPoints.push_back(i);

    return articulationPoints;
}