using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Node root = GetNodes();

        //root = InsertAtBegining(root, -1);

        root = InsertAtEnd(root, 10);

        root = InsertAtEnd(root, 11);

        TravarseNodes(root);

        TravarseNodesReverse(root);

    }

    public static Node GetNodes()

    {

        Node rootNode = new Node();

            rootNode.Data = 0;

        Node lastNode = rootNode;

        for(var i=1; i < 10; i++)

        {

            Node newNode = new Node();

                 newNode.Data = i;

                 newNode.Prev = lastNode;

            lastNode.Next = newNode;

            lastNode = newNode;

        }

        lastNode.Next = rootNode;

        rootNode.Prev = lastNode;

        return rootNode;

    }

    public static void TravarseNodes(Node root)

    {

            Console.Write(root.Data + " "); 

            Node tempRoot = root.Next;

            while(tempRoot != root)

            {

                Console.Write(tempRoot.Data + " "); 

                tempRoot = tempRoot.Next;

            }

            Console.WriteLine();

    }

    public static void TravarseNodesReverse(Node root)

    {

            Node lastNode = root.Prev;

            while(lastNode != root)

            {

                Console.Write(lastNode.Data + " " );

                lastNode = lastNode.Prev;

            }

            Console.Write(root.Data + " " );

            Console.WriteLine();        

    }

    public static Node InsertAtBegining(Node root, int data)

    {

        Node newNode = new Node();

             newNode.Data = data;

             newNode.Next = root;

        Node tempRootPrev = root.Prev;

        root.Prev = newNode;

        tempRootPrev.Next = newNode;

        newNode.Prev = tempRootPrev;

        return newNode;

    }

    public static Node InsertAtEnd(Node root, int data)

    {

        Node newNode = new Node();

             newNode.Data = data;

             newNode.Next = root;

             newNode.Prev = root.Prev;

        root.Prev.Next = newNode;

        root.Prev = newNode;

​

        return root;

    }

}

​

public class Node

{

    public int Data { get; set; }

    public Node Next { get; set; }

    public Node Prev { get; set; }

}

​

​

​