graph - Articulation point

// Articulation Point of a graph. O(V+E).
int Time[N] , low[N];
int dfn= 0;
void dfs(int u,int p )
{
      Time[u] = low[u] = dfn ++;
      vis[u]=1;
      int cnt = 0;
      for(auto a: G[u]) {
            if(a==p) continue;
            if(vis[a]) {
                  low[u] = min(low[u] , Time[a]);
            }
            else {
                  dfs(a,u);
                  if(low[a] >= Time[u] ) {
                        isAp[u]=1;
                  }
                  low[u] = min(low[u] , low[a]);
                  cnt ++;
            }
      }
      if(p==-1) {
            isAp[u] = (cnt>1);
      }

}