using System;

    using System.Collections.Generic;

    using System.Linq;

    using System.Text;

    using System.Threading.Tasks;

​

    namespace ConsoleApp1

    {

        class Program

        {

            public int[] cache = new int[3];

            public int[] MemoryArray ;

​

             static void Main(string[] args)

            {

                Program obj = new Program();

                int lenght;

​

                Console.Write("Enter length of an array : ");

                lenght = Convert.ToInt32(Console.ReadLine());

                Console.WriteLine("array length : {0}", lenght);

​

                obj.MemoryArray = new int[lenght];

​

                Console.WriteLine("Enter number in array : ");

​

                for (int i = 0; i < obj.MemoryArray.Length; i++)

                {

                    int a = 0;

                    a = Convert.ToInt32(Console.ReadLine());

                    obj.MemoryArray[i] = a ;

                }

​

                //array = myString.ToCharArray();

​

                if (obj.MemoryArray.Length <= 0)

                {

                    Console.WriteLine("Enter minimum one arguments....");

                    return;

                }

​

                obj.initiallize();

                obj.serviceRequest();

​

                Console.ReadKey();

​

            }

​

            //initializes the cache with the first three elements in the array

​

            void initiallize()

            {

                if (MemoryArray.Length < 3)

                {

                    for (int i = 0; i < MemoryArray.Length; i++)

                    {

                        cache[i] = MemoryArray[i];

                    }

                }

                else

                {

                    for (int i = 0; i < cache.Length; i++)

                    {

                        cache[i] = MemoryArray[i];

                    }

                }

            }

​

            bool wasInCache(int key)

            {

                for (int i = 0; i < cache.Length; i++)

                {

                    if (cache[i] == key)

                    {

                        return true;

                    }

                }

                return false;

            }

​

            // if the request was not in the cache, this updates the cache to include it

            // removes the request in the cache that is "farthest in future"

​

            void updateCache(int x, int index)

            {

                int one = 0;

                int two = 0;

                int three = 0;

​

                for (int i = 0; i < MemoryArray.Length; i++)

                {

                    //checks where the cache element appears first again in the request array and 

                    //puts the index in it's respective variable if the variable is still 0

​

                    if (cache[0] == MemoryArray[i] && one == 0)

                    {

                        one = i;

                    }

                    if (cache[1] == MemoryArray[i] && one == 0)

                    {

                        two = i;

                    }

                    if (cache[2] == MemoryArray[i] && one == 0)

                    {

                        three = i;

                    }

                }

​

                // if any of the indexes are still 0, that cache place is the one to get replaced 

​

                if (one == 0)

                {

                    cache[0] = x;

                }

                else if (two == 0)

                {

                    cache[1] = x;

                }

                else if (three == 0)

                {

                    cache[2] = x;

                }

​

                //otherwise, it checks whichever index is the largest and sets the respective cache

                //place to the new variable

​

                else

                {

                    if ((one > two && one > three) || one == 0)

                    {

                        cache[0] = x;

                    }

                    else if (two > one && two > three)

                    {

                        cache[1] = x;

                    }

                    else if (three > one && three > two)

                    {

                        cache[2] = x;

                    }

                }

            }

​

            // completes the request and updates the hit and miss count

​

            void serviceRequest()

            {

                int hitCount = 0;

                int missCount = 0;

​

                for (int i = 3; i < MemoryArray.Length; i++)

                {

                    Console.WriteLine("Right now values in cache: " + cache[0] + " " + cache[1] + " " + cache[2]);

                    if (wasInCache(MemoryArray[i]))

                    {

                        hitCount++;

                    }

                    else

                    {

                        missCount++;

                        updateCache(MemoryArray[i], i);

                    }

                }

                Console.WriteLine("Total Hit counts = " + hitCount);

                Console.WriteLine("Total miss counts = " + missCount);

            }

        }

    }

​

​