using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var G = new Dictionary<string, string[]>(); 

        G.Add("A", new string[] {"B", "C"} );

        G.Add("B", new string[] {"A", "D", "E"} );

        G.Add("C", new string[] {"A", "E"} );

        G.Add("G", new string[] {"H", "I"});

        G.Add("H", new string[] {"G", "I"});

        G.Add("I", new string[] {"H", "G"});        

        G.Add("D", new string[] {"B", "E"} );

        G.Add("E", new string[] {"B", "C"} );       

        Console.WriteLine(G.Count);

        Console.WriteLine("Run BFS, starting with C");      

        BFS(G, "C");

        Console.WriteLine("Run BFS, starting with H");

        BFS(G, "H");

    }

    public static void BFS(Dictionary<string, string[]> g, string s) 

    {

        var Q = new Queue<string>();

        var keys = g.Keys;

        // Initialize explored list

        var explored = new Dictionary<string, bool>();

        foreach (string key in keys) {

            explored[key] = false;

        }

        explored[s] = true;     

        Console.WriteLine("found " + s);

        Q.Enqueue(s);

        while (Q.Count > 0)

        {

            string v = Q.Dequeue();

            foreach (string w in g[v]) 

            {

                if (!explored[w])

                    {

                        explored[w]=true;

                        Console.WriteLine("found " + w);

                        Q.Enqueue(w);

                    } // if

            }  //for 

        }  // while

​

    }

}