Question

I made a simple program in C# to add a node in binary tree.
I have an object field ‘Root’ to hold the main parent Node. such that every time I add a node I traverse from the tree by retrieving the data in Parent Node.

Here is my code

public class BTNode
    {
        public int Value { get; set; }        
        public BTNode Left { get; set; }
        public BTNode Right { get; set; }
        public BTNode Root { get; set; }
   }


public class BinaryTree
   {
       public  BinaryTree()
        {
            size = 0;
            Root = null; //To hold the main Parent Node
         }
        int size;
        object Root;

        public void AddNode(int value)
        {
            BTNode NewNode = new BTNode();
            if (Root != null)
            {
                NewNode = (BTNode)Root; //If tree exists, Get the Root Node
            }

            while (NewNode.Root != null)
            {
                if (value < NewNode.Value)
                {
                    NewNode.Root = NewNode.Left;
                }
                else if (value > NewNode.Value)
                {
                    NewNode.Root = NewNode.Right;
                }
            }

            size++;
            NewNode.Value = value;   //OBJECT 'ROOT' GETTING UPDATED AT THIS POINT
            NewNode.Root = NewNode;  //self pointer 
            NewNode.Left = null;
            NewNode.Right = null;

            if (size == 1)
            {
                Root = (object) NewNode;  //if this is the Parent Node(First Node) 
            }                             //then update the Root to be the parent Node
        }
    }

I want to hold only parent node of the Binary Tree in ‘Root’.. I only want to execute the last line when size =1 i.e if its the first node of the tree but no matter what I do the Root gets updated for every node. I am struggling to know why this is happening, Please help me. am I missing any concpept, logic here.

Answer 1

1. Your Root property could be typed to BTNode. This way you wouldn’t need to cast it
2. The line NewNode = (BTNode)Root; is getting the root node reference. Any change you make to NewNode will affect the root node. Are you aware of value types and reference types?
3. I don’t understand why you’re going up (checking for the Root) and not down (checking for the Left or Right nodes).

Check this solution, please. It uses a simple recursive method to place the new node:

public class BinaryTree
    {
        public BinaryTree()
        {
            size = 0;
            Root = null; //To hold the main Parent Node
        }
        int size;
        BTNode Root;

        public void AddNode(int value)
        {
            size++;
            BTNode NewNode = new BTNode()
            {
                Value = value
            };

            if (this.Root == null)
            {
                this.Root = NewNode;
                return;
            }

            this.PlaceNewNode(this.Root, NewNode);
        }

        public void PlaceNewNode(BTNode RootNode, BTNode NewNode)
        {
            if (NewNode.Value < RootNode.Value)
            {
                if (RootNode.Left != null)
                {
                    PlaceNewNode(RootNode.Left, NewNode);
                }
                else
                {
                    RootNode.Left = NewNode;
                    return;
                }
            }
            else
            {
                if (RootNode.Right != null)
                {
                    PlaceNewNode(RootNode.Right, NewNode);
                }
                else
                {
                    RootNode.Right = NewNode;
                    return;
                }
            }
        }
    }

Hope this helps.

Regards