ALGR: Articulation Node

#include<iostream>
#include<cstdio>
#include<vector>
#define MAX_NODE 10000
#define NIL 99999
using namespace std;

vector<bool> visited(MAX_NODE,false);
vector<bool> Articulations_pont(MAX_NODE);
vector<int> parent(MAX_NODE,-1);
int time=0;
vector<int> d(MAX_NODE,0);
vector<int> low(MAX_NODE,0);


void DFS_Visit(vector<vector<int>> gr, int u) // taking reference to see the changes in color
{
    time++;
    d[u]=time;//cout<<"start time of "<<u<<" is "<<d[u]<<endl;
    low[u]=d[u];
    visited[u]=true;
    int num_of_childeren_visited=0;
    for(int i=0; i<gr[u].size(); i++)
    {

        int v=gr[u][i];
        bool flag = false;
        if(v==parent[u])
        {
            ///go to line (what??)
            flag = true;
        }
        if(!flag)
        {
            if(visited[v]==true)
            {
                low[u]=min(low[u],d[v]);
            }
            if(!visited[v])
            {
                parent[v]=u;
                DFS_Visit(gr,v);
                low[u]=min(low[u],low[v]);

                if(d[u]<=low[v] && parent[u]!=-1)// when u is root, parent[u]=-1
                    Articulations_pont[u]=true;
                num_of_childeren_visited++;
            }
            if(num_of_childeren_visited>1 && parent[u]==-1)
                Articulations_pont[u]=true;
        }
    }//end for
}
void DFS(vector<vector<int>> gr)
{
    int nv = gr.size() - 1;
//    for(int i=1;i<=nv;i++){
//        visited[i]=false;
//        parent[i]=-1;
//        d[i]=0;
//        low[i]=0;
//    }
    //time=0;
    for(int i=1; i<=nv; i++)
        if(!visited[i])
            DFS_Visit(gr,i);
}

int main()
{
    int n, e;
    scanf("%d %d", &n, &e);
    vector<vector<int>> gr;
    gr.clear();
    gr.resize(n+1);
    for(int i=0; i<e; i++)
    {
        int u,v;
        scanf("%d %d", &u, &v);
        gr[u].push_back(v);
        gr[v].push_back(u);
    }

    DFS(gr);
    printf("Articulation points are :\n");
    for(int i=1; i<n; i++)
        if(Articulations_pont[i]==true)
            cout<<i<<endl;
    return 0;
}