BFS-Graph_using-QUEUE.cpp

#include <bits/stdc++.h>
using namespace std;

class Graph
{
private:
    int v;
    list<int> *graph;

public:
    Graph(int v)
    {
        this->v = v;
        graph = new list<int>[v];
    }

    void addEdges(int e1, int e2)
    {
        graph[e1].push_back(e2);
        graph[e2].push_back(e1);
    }

    void display(int v)
    {
        cout << "List representation of the graph is : " << endl;
        for (int i = 0; i < v; i++)
        {
            cout << i << " --> ";

            for (auto v : graph[i])
                cout << i << "  ";
            cout << endl;
        }
    }

    void BFS(int source)
    {
        vector<int> visited(v, 0);
        queue<int> q;

        cout << source << "  ";
        q.push(source);

        visited[source] = 1;

        while (!q.empty())
        {
            int front = q.front();
            q.pop();

            for (auto v : graph[front])
            {
                if (!visited[v])
                {
                    cout << v << "  ";
                    visited[v] = 1;
                    q.push(v);
                }
            }
        }
    }
};

int main()
{
    int v = 4;
    Graph g(v);

    g.addEdges(0, 1);
    g.addEdges(0, 2);
    g.addEdges(1, 2);
    g.addEdges(2, 3);

    g.display(v);

    int source = 0;

    cout << "BFS of the graph is : ";
    g.BFS(source);

    return 0;
}