4.2 Check existance of path between 2 nodes of a tree.cpp

//C++ Program to check and find if the path between two nodes exists

#include <iostream>
#include <list>

using namespace std;

class Graph
{
        int V; 
        list<int> *adj; 
    public:
        Graph(int V); 
        void addEdge(int v, int w); 
        bool isReachable(int s, int d); ]
};

Graph::Graph(int V)
{
    this->V = V;
    adj = new list<int> [V];
}

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


bool Graph::isReachable(int s, int d)
{
    if (s == d)
        return true;
    bool *visited = new bool[V];
    for (int i = 0; i < V; i++)
        visited[i] = false;
    list<int> queue;
    visited[s] = true;
    queue.push_back(s);
    list<int>::iterator i;
    while (!queue.empty())
    {
        s = queue.front();
        queue.pop_front();
        for (i = adj[s].begin(); i != adj[s].end(); ++i)
        {
            if (*i == d)
                return true;
            if (!visited[*i])
            {
                visited[*i] = true;
                queue.push_back(*i);
            }
        }
    }
    return false;
}

int main()
{
    Graph g(4);
    g.addEdge(0, 1);
    g.addEdge(0, 2);
    g.addEdge(1, 2);
    g.addEdge(2, 0);
    g.addEdge(2, 3);
    g.addEdge(3, 3);
    cout << "Enter the source and destination vertices: (0-3)";
    int u, v;
    cin >> u >> v;
    if (g.isReachable(u, v))
        cout << "\nThere is a path from " << u << " to " << v;
    else
        cout << "\nThere is no path from " << u << " to " << v;
    int temp;
    temp = u;
    u = v;
    v = temp;
    if (g.isReachable(u, v))
        cout << "\nThere is a path from " << u << " to " << v;
    else
        cout << "\nThere is no path from " << u << " to " << v;
    return 0;
}