using System;

using System.Collections;

​

public class Node

{

    public int data;

    public Node left;

    public Node right;

    public Node(int d)

    {

        data=d;

        left=right=null;

    }

}

​

public class BinaryTree

{

    Node root;

    public static void Main()

    {   

        BinaryTree tree = new BinaryTree();

        tree.root = new Node(1);

        tree.root.left = new Node(2);

        tree.root.right = new Node(3);

        tree.root.left.left = new Node(4);

        tree.root.left.right = new Node(5);

        tree.Preorder();

    }

    public void Preorder()

    {

        Node current = root;

        Stack s = new Stack();

        s.Push(root);

        while(s.Count>0)

        {

            current=(Node) s.Pop();

            Console.WriteLine(current.data);

            if(current.right!=null)

            {

                s.Push(current.right);

            }

            if(current.left!=null)

            {

                s.Push(current.left);

            }

        }

    }

}