using System;

public class Program

{

    public static void Main()

    {

            ListFromTree obj = new ListFromTree();

            obj.Run();

    }

}

​

​

  public class ListFromTree

    {

​

        public static Node generalNode = new Node();

        public Node prev = generalNode;

​

        public void Run() {

            Node result = FlatTree(createTree());

        }

​

        public Node FlatTree(Node root) {

            if (root == null)

            {

                return null;

            }

            FlatTree(root.Left);

​

            Node rightNode = root.Right;

            prev.Left = null;

            prev.Right = root;

            prev = root;

​

            FlatTree(rightNode);

​

            return generalNode.Right;

        }

​

​

        public Node createTree() {

            return new Node()

            {

                Data = 10,

                Left = new Node()

                {

                    Data = 7,

                    Left = new Node

                    {

                        Data = 6,

                    },

                    Right = new Node

                    {

                        Data = 8

                    }

                },

                Right = new Node

                {

                    Data = 12,

                    Left = new Node()

                    {

                        Data = 11

                    },

                    Right = new Node()

                    {

                        Data = 13

                    }

                }

​

            };

        }

    }

​

​

    public class Node {

        public Node Left;

        public Node Right;

        public int Data;

    }