Binary Search Tree insertion & inorder

User_AYF65

Hi,

I have written a program to insert values in a binary search tree and print the values using inorder traversal. Following is my code:

class TreeNode{

   int data;

   TreeNode left;

   TreeNode right;

   TreeNode(int data1, TreeNode l, TreeNode r){

      data = data1;

      left = l;

      right =r;

   }

}

class bst1{

   TreeNode root;

   bst1( ) {

      root = null;

   }

 

   public static void main(String[ ] args){

       

        bst1 obj = new bst1();

  int[ ] arr= {90, 75, 10, 20, 30, 40, 50, 70};

        for(int i=0; i<8; ++i)

        obj.root= obj.insert(arr[i], obj.root);

        obj.inorder (obj.root);

   }

   TreeNode insert(int data, TreeNode t){

      if(t ==null) {

         t = new TreeNode(data, null, null);

      }

      else if(t.data<data){

         t.right = insert(t.data, t.right);

      }

      else

         t.left = insert(t.data, t.left);

      return t;

  }

    private void inorder(TreeNode r)

  {

  if(r !=null)

  {

  inorder(r.left);

  System.out.print(r.data +" ");

  inorder(r.right);

  }

       }

}

Can somebody please guide me what's the problem with my code. Its printing only the first node.

>javac bst1.java

>java bst1

90 90 90 90 90 90 90 90

>

Zulfi.

TPD-Opitz

Thanks for Posting an SSCCE.

The problem is here:

TreeNode insert(int data, TreeNode t) {
        if (t == null) {
            t = new TreeNode(data, null, null);
        } else if (t.data < data) {
            t.right = insert(t.data, t.right);
        } else {
            t.left = insert(t.data, t.left);
        }
        return t;
    }

You pass the data of the parent node instead of the new value to the child creation.

better is this

TreeNode insert(int data, TreeNode t) {
        if (t == null) {
            t = new TreeNode(data, null, null);
        } else if (t.data < data) {
            t.right = insert(data, t.right);
        } else {
            t.left = insert(data, t.left);
        }
        return t;
    }

And the best solution was to choose meaningfull names for your identifiers:

TreeNode appendNewNode(int newData, TreeNode currentNode) {
        if (currentNode == null) {
            currentNode = new TreeNode(newData, null, null);
        } else if (currentNode.data < newData) {
            currentNode.right = appendNewNode(newData, currentNode.right);
        } else {
            currentNode.left = appendNewNode(newData, currentNode.left);
        }
        return currentNode;
    }

bye

TPD