using System;

using System.Collections.Generic;

public class Program

{

    public class TreeNode<T>{

        public T Data {get; set;}

        public TreeNode<T> Left {get; set;}

        public TreeNode<T> Right {get; set;}

        public TreeNode(T data){

            this.Data = data;

        }

    }

    /*public static TreeNode<int> CreateBST(){

        var rootNode = new TreeNode<int>(10){

            Left = new TreeNode<int>(3),

            Right = new TreeNode<int>(12)

        };

        return rootNode;

    }*/

    public static TreeNode<int> CreateBST(){

        var rootNode = new TreeNode<int>(10){

            Left = new TreeNode<int>(3){

                Left = new TreeNode<int>(2),

                Right = new TreeNode<int>(5){

                    Right = new TreeNode<int>(6)

                }

            },

            Right = new TreeNode<int>(12){

                Left = new TreeNode<int>(11),

                Right = new TreeNode<int>(20){

                    Left = new TreeNode<int>(14)

                }

            }

        };

        return rootNode;

    }

    public static void PrintSequences(List<List<int>> seqs){

        foreach(var seq in seqs){

            foreach(var elm in seq){

                Console.Write(elm + " ");

            }

            Console.WriteLine();

        }

    }

    private static void BST_Sequences(List<TreeNode<int>> options, List<int> currSeq, List<List<int>> seqs){

        if (options.Count == 0){

            seqs.Add(new List<int>(currSeq));

            return;

        }

        foreach (var option in options){

            currSeq.Add(option.Data);

            var newOptions = new List<TreeNode<int>>(options);

            newOptions.Remove(option);

            if (option.Left != null) newOptions.Add(option.Left);

            if (option.Right != null) newOptions.Add(option.Right);

            BST_Sequences(newOptions, currSeq, seqs);

            currSeq.Remove(option.Data);

        }

    }

    public static List<List<int>> BST_Sequences(TreeNode<int> node){

        var seqs = new List<List<int>>();

        var options = new List<TreeNode<int>>(){node};

        var currSeq = new List<int>();

        BST_Sequences(options, currSeq, seqs);

        return seqs;

    }

    public static void Main()

    {

        var seqs = BST_Sequences(CreateBST());

        PrintSequences(seqs);

    }

}