Insert function dosen't insert

Question

Ive starting learning C# with a background of c/c++. I am creating a simple BST but my insert function wont work. Any help would greatly be appreciated.

I get this kind of error when not passing by reference in c/c++. Since I created a two classes Node and BST, shouldn't they be passed by reference? Ive worked on this problem for a couple of hours and tried to change my code but with no luck.

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

    public Node Left
    {
        get { return left; }
        set { left = value; }
    }

    public Node Right
    {
        get { return right; }
        set { right = value; }
    }

    public int Data
    {
        get { return data; }
        set { data = value; }
    }


}

class BST
{
    private Node root;

    public BST()
    {
        root = null;
    }

    public Node Root
    {
        get { return root; }
        set { root = value; }
    }

    public void Insert(int data)
    {
        if (root == null)
        {
            root = new Node(data);

        }
        else
        {
            InsertHelper(root, data);

        }
    }

    public void InsertHelper( Node root, int data)
    {
        if (root == null)
        {
            root = new Node(data);
            //return root;
        }

        if (root.Data > data)
        {
             InsertHelper(root.Left, data);
        }

        if (root.Data < data)
        {
             InsertHelper(root.Right, data);
        }

    }

Answer 1

You are assigning a new node to the argument pointer instead of original one. Insert should be:

  public void Insert(int data)
    {
        if (root == null)
        {
            root = new Node(data);

        }
        else
        {
            root = InsertHelper(root, data);

        }
    }

and InsertHelper should be:

public Node InsertHelper( Node root, int data)
    {
        if (root == null)

            return new Node(data);



        if (root.Data > data)
        {
             root.Left = InsertHelper(root.Left, data);
        }

        if (root.Data < data)
        {
             root.Right = InsertHelper(root.Right, data);
        }

        return root;

    }

In fact you don't even need Insert since InsertHelper already deals with root being null

Main method for testing:

public static void Main()
    {


        BST bst = new BST();


        bst.Insert(5);
        bst.Insert(6);
        bst.Insert(4);
        bst.Insert(7);
        bst.Insert(3);

        Console.WriteLine(bst.Root.Data + " ");
        Console.WriteLine(bst.Root.Left.Data + " ");
        Console.WriteLine(bst.Root.Right.Data + " ");
        Console.WriteLine(bst.Root.Left.Left.Data + " ");
        Console.WriteLine(bst.Root.Right.Right.Data + " ");


    }