using System;

using System.Threading;

public class Program

{

    public static int[] a = new int[3];

    public static int misses = 0;

    public static int allgood = 0;

    public static object mutex = new object();

​

    public static void foo()

    {

        // new reference object incoming

        int[] b = new int[3];

        Array.Copy(a, b, 3);

        Random r = new Random();

        for(int i = 0; i < 1000000; i++)

        {

            b[0] += 10;

            b[1] += 10;

            b[2] += 10;

            // atomic reference assignment

            lock(mutex)

            {

                a = b;

                //At this point , both a and b are now pointing to the same allocation of 3 integers.

                //With this hint, can you fix it? :) 

            }

        }

    }

    public static int[] bar()

    {

        lock(mutex)

        {

        return a;

        }

    }

    public static void alice()

    {

        for(int i = 0; i < 1000000; i++)

        {

            int[] c = bar();

            if (c[0] != c[2])

            {

                misses++;

                Console.WriteLine("MISS c[0]: {0} c[2]: {1}", c[0], c[2]);

            }

            else

            {

                allgood++;

            }

        }

    }

    public static void Main()

    {

        Thread first = new Thread(new ThreadStart(foo));

        Thread second = new Thread(new ThreadStart(alice));

        first.Start();

        second.Start();

        Console.WriteLine("main, foo and bar now execute concurrently...");

        first.Join();

        second.Join();

        Console.WriteLine("misses: {0}  allgood: {1}", misses, allgood);

        Console.WriteLine("foo and bar completed....");

    }

}