Bai2_Graph_HCMUT

#include<iostream>
#include <list>
using namespace std;

class DirectedGraph
{
    int V;
    list<int> *adj;
    bool isCyclicUtil(int v, bool visited[], bool *rs);
public:
    DirectedGraph(){
        V = 0;
        adj = NULL;
    }
    DirectedGraph(int V)
    {
        this->V = V;
        adj = new list<int>[V];
    }
    void addEdge(int v, int w)
    {
        adj[v].push_back(w);
    }
    bool isCyclic()
    {
            // Mark all the vertices as not visited and not part of recursion
    // stack
    bool *visited = new bool[V];
    bool *recStack = new bool[V];
    for(int i = 0; i < V; i++)
    {
        visited[i] = false;
        recStack[i] = false;
    }

    // Call the recursive helper function to detect cycle in different
    // DFS trees
    for(int i = 0; i < V; i++)
        if (isCyclicUtil(i, visited, recStack))
            return true;

    return false;
    }
};
      bool  DirectedGraph::isCyclicUtil(int v, bool visited[], bool *recStack)
{
    if(visited[v] == false)
    {
        // Mark the current node as visited and part of recursion stack
        visited[v] = true;
        recStack[v] = true;

        // Recur for all the vertices adjacent to this vertex
        list<int>::iterator i;
        for(i = adj[v].begin(); i != adj[v].end(); ++i)
        {
            if ( !visited[*i] && isCyclicUtil(*i, visited, recStack) )
                return true;
            else if (recStack[*i])
                return true;
        }

    }
    recStack[v] = false; // remove the vertex from recursion stack
    return false;
}