using System;

using System.Collections;

using System.Collections.Generic;

public class Program

    {

        public static void Main(string[] args)

        {

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

            Stack<int> s = new Stack<int>();

​

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

​

            queue.Enqueue(1);

            queue.Enqueue(2);

            queue.Enqueue(3);

​

            var value = queue.Dequeue();

​

            while (value != 0)

            {

                Console.WriteLine("Queued value: {0}", value);

​

                value = queue.Dequeue();

            }

​

            CustomStack<int> stack = new CustomStack<int>();

​

            stack.Push(1);

            stack.Push(2);

            stack.Push(3);

​

            value = stack.Pop();

​

            while (value != 0)

            {

                Console.WriteLine("Stack value: {0}", value);

​

                value = stack.Pop();

            }

​

            Console.ReadLine();

        }

​

        private class CustomQueue<TObject> : IEnumerable<TObject>

        {

            LinkedList<TObject> list = new LinkedList<TObject>();

            public IEnumerator<TObject> GetEnumerator() { return list.GetEnumerator(); }

            IEnumerator IEnumerable.GetEnumerator() { return this.GetEnumerator(); }

​

            public TObject Dequeue()

            {

                var result = list.First;

                if (result != null)

                {

                    list.Remove(result);

                    return result.Value;

                }

                else

                {

                    return default(TObject);

                }

            }

​

            public void Enqueue(TObject item)

            {

                if (list.Last == null)

                {

                    list.AddFirst(item);

                }

                else

                {

                    list.AddAfter(list.Last, item);

                }

            }

        }

        private class CustomStack<TObject> : IEnumerable<TObject>

        {

            LinkedList<TObject> list = new LinkedList<TObject>();

            public IEnumerator<TObject> GetEnumerator() { return list.GetEnumerator(); }

            IEnumerator IEnumerable.GetEnumerator() { return this.GetEnumerator(); }

​

            public TObject Pop()

            {

                var result = list.Last;

                if (result != null)

                {

                    list.Remove(result);

                    return result.Value;

                }

                else

                {

                    return default(TObject);

                }

            }

​

            public void Push(TObject item)

            {

                if (list.Last == null)

                {

                    list.AddFirst(item);

                }

                else

                {

                    list.AddAfter(list.Last, item);

                }

            }

        }

    }