using System;

public class Program

    {

        public static void Main(string[] args)

        {

            var first = new Node(1);

            first.Push(2).Push(3).Push(4).Push(5);

            first.Print();

            DeleteAlternate(first);

            Console.WriteLine("=============== After swapping ===============");

            first.Print();

        }

​

        static void DeleteAlternate(Node first)

        {

            var node = first;

            while (node?.Next?.Next != null)

            {

                node.Next = node.Next.Next;

                node = node.Next;

            }

            if (node?.Next != null && node.Next.Next == null)

            {

                node.Next = null;

            }

        }

    }

​

    public class Node

    {

        public int Data { get; set; }

        public Node Next { get; set; }

        public Node(int data)

        {

            this.Data = data;

            this.Next = null;

        }

​

        public void Print()

        {

            var node = this;

            do

            {

                Console.Write(node.Data);

                node = node.Next;

            } while (node != null);

            Console.WriteLine();

        }

​

        public int GetLengthIterative()

        {

            var node = this;

            var count = 0;

            while (node != null)

            {

                count++;

                node = node.Next;

            }

            return count;

        }

​

        public int GetLengthRecursive()

        {

            if (this.Next == null)

            {

                return 1;

            }

            return 1 + this.Next.GetLengthRecursive();

        }

​

        public Node Push(int data)

        {

            var node = new Node(data);

            this.Next = node;

            return node;

        }

​

        public override string ToString()

        {

            return Data.ToString();

        }

    }