Binary Search Tree in C# Implementation

Question

class Node
{
    public int data;
    public Node left, right;

    public Node(int data)
    {
        this.data = data;
        left = null;
        right = null;

    }
}

class BinaryTreeImp
{
    Node root;
    static int count = 0;

    public BinaryTreeImp()
    {
        root = null;

    }
    public Node addNode(int data)
    { 
        Node newNode = new Node(data);

        if (root == null)
        {
            root = newNode;

        }
        count++;
        return newNode;


    }

    public void insertNode(Node root,Node newNode )
    {
        Node temp;
        temp = root;

        if (newNode.data < temp.data)
            {
                if (temp.left == null)
                {
                    temp.left = newNode;

                }

                else
                {
                    temp = temp.left;
                    insertNode(temp,newNode);

                }
            }
            else if (newNode.data > temp.data)
            {
                if (temp.right == null)
                {
                    temp.right = newNode;

                }

                else 
                {
                    temp = temp.right;
                    insertNode(temp,newNode);
                }
            }
        }


    public void displayTree(Node root)
    {
        Node temp;
        temp = root;

        if (temp == null)
            return;
            displayTree(temp.left);
            System.Console.Write(temp.data + " ");
            displayTree(temp.right);


    }

    static void Main(string[] args)
    {
       BinaryTreeImp btObj = new BinaryTreeImp();
       Node iniRoot= btObj.addNode(5);


       btObj.insertNode(btObj.root,iniRoot);
       btObj.insertNode(btObj.root,btObj.addNode(6));
       btObj.insertNode(btObj.root,btObj.addNode(10));
       btObj.insertNode(btObj.root,btObj.addNode(2));
       btObj.insertNode(btObj.root,btObj.addNode(3));
       btObj.displayTree(btObj.root);

       System.Console.WriteLine("The sum of nodes are " + count);
       Console.ReadLine();

    }
}

This is the code for implementation.The code works fine but if in the displayTree function , i replace it with

public void displayTree(Node root)
{
    Node temp;
    temp = root;

    while(temp!=null)
    {
        displayTree(temp.left);
        System.Console.Write(temp.data + " ");
        displayTree(temp.right);
    }

}

an infinite loop is caused. I don't understand what is causing this.Also i would like to know if there is a better way of implementing a BST in C#.

Answer 1

I'm not sure why you need this loop, but answering your question:

while(temp!=null)
{
    displayTree(temp.left);
    System.Console.Write(temp.data + " ");
    displayTree(temp.right);
}

this code checks if temp is not null, but it will never become null, cause inside the loop you act only on the leafs of the temp. That's why you have an infinit loop.

Answer 2

You don't need a while loop nor a temp variable, let recursion do the work for you:

public void displayTree(Node root)
{
    if(root == null) return;

    displayTree(root.left);
    System.Console.Write(root.data + " ");
    displayTree(root.right);
}