using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Queue<int> que = new Queue<int>();

        Graph g = new Graph(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);

        g.BFS(2);

    }

}

​

public class Graph

{

    int V; //no of vertices

    List<int>[] adj;

    public Graph(int v)

    {

        V = v;

        adj = new List<int>[v];

        for (int i = 0; i < v; i++)

        {

            adj[i] = new List<int>();

        }

    }

​

    public void addEdge(int v, int w)

    {

        adj[v].Add(w);

    }

​

    public void BFS(int s)

    {

        bool[] visited = new bool[V];

        for (int i = 0; i < V; i++)

            visited[i] = false;

        Queue<int> queue = new Queue<int>();

        queue.Enqueue(s);

        visited[s] = true;

        while (queue.Count != 0)

        {

            int pop = queue.Dequeue();

            Console.Write(pop + " ");

            foreach (var vert in adj[pop])

            {

                if (!visited[vert])

                {

                    visited[vert] = true;

                    queue.Enqueue(vert);

                }

            }

        }

    }

}