using System;

using System.Collections;

using System.Collections.Generic;

public class Program

{

    public class Node<T>

    {

        public Node(T data)

        {

            Data = data;

        }

        public T Data { get; set; }

        public Node<T> Next { get; set; }

    }

​

    public class LinckedList<T> : IEnumerable<T>

    {

        public Node<T> head;

        public int count;

​

        public void Push(T data)

        {

            Node<T> node = new Node<T>(data);

            if(head != null)

            {

                node.Next = head;

                head = node;

                count++;

            }

            else

            {

                head = node;

                count++;

            }

        }

​

        public bool Pop()

        {

            if(head != null)

            {

                if(head.Next != null)

                {

                    head = head.Next;

                    count--;

                }

                else

                {

                    head = null;

                    count--;

                }

                return true;

            }

            return false;

        }

​

        public T Peek()

        {

            if(head != null)

            {

                return head.Data;

            }

            else

            {

                throw new InvalidOperationException(); 

            }

        }

​

        IEnumerator IEnumerable.GetEnumerator()

        {

            return ((IEnumerable)this).GetEnumerator();

        }

​

        IEnumerator<T> IEnumerable<T>.GetEnumerator()

        {

            Node<T> current = head;

            while (current != null)

            {

                yield return current.Data;

                current = current.Next;

            }

        }

    }

    public static void Main()

    {

        LinckedList<string> linckedList = new LinckedList<string>();

            linckedList.Push("Apple");

            linckedList.Push("Samsung");

            linckedList.Push("Nokia");

            linckedList.Push("LG");

            linckedList.Pop();

            linckedList.Pop();

            var peek = linckedList.Peek();

​

            foreach (string node in linckedList)

            {

                Console.WriteLine(node); 

            }

​

            Console.WriteLine("Вершина стека: " + peek);

            Console.ReadLine();

    }

}