algorithms/Connected_Dfs.cpp at master · notepad104/algorithms · GitHub

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

class Graph
{
    private:
        int V;
        list<int> *adj;
        void DFSUtil(int v, bool visited[]);
    public:
    Graph(int V)
    {
        this->V = V;
        adj = new list<int>[V];
    }
    ~Graph()
    {
        delete [] adj;
    }
    void addEdge(int v, int w);
    bool isConnected();
    Graph getTranspose();
};

// A recursive function to print DFS starting from v
void Graph::DFSUtil(int v, bool visited[])
{
    visited[v] = true;
    list<int>::iterator i;
    for (i = adj[v].begin(); i != adj[v].end(); ++i)
        if (!visited[*i])
            DFSUtil(*i, visited);
}

// Function that returns reverse (or transpose) of this graph
Graph Graph::getTranspose()
{
    Graph g(V);
    for (int v = 0; v < V; v++)
    {
        list<int>::iterator i;
        for(i = adj[v].begin(); i != adj[v].end(); ++i)
        {
            g.adj[*i].push_back(v);
        }
    }
    return g;
}

void Graph::addEdge(int v, int w)
{
    adj[v].push_back(w);

}

bool Graph::isConnected()
{
    bool visited[V];
    for (int i = 0; i < V; i++)
        visited[i] = false;
    DFSUtil(0, visited);
    for (int i = 0; i < V; i++)
        if (visited[i] == false)
             return false;
    Graph gr = getTranspose();
    for(int i = 0; i < V; i++)
        visited[i] = false;
    gr.DFSUtil(0, visited);
    for (int i = 0; i < V; i++)
        if (visited[i] == false)
             return false;
    return true;
}

int main()
{
    Graph g1(5);
    g1.addEdge(0, 1);
    g1.addEdge(1, 2);
    g1.addEdge(2, 3);
    g1.addEdge(3, 0);
    g1.addEdge(2, 4);
    g1.addEdge(4, 2);
    g1.isConnected()? cout << "Yes\n" : cout << "No\n";

    Graph g2(4);
    g2.addEdge(0, 1);
    g2.addEdge(1, 2);
    g2.addEdge(2, 3);
    g2.isConnected()? cout << "Yes\n" : cout << "No\n";


    return 0;
}