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Program: Find height of a Binary Search Tree (BST)


For a binary tree to be a binary search tree (BST), the data of all the nodes in the left sub-tree of the root node should be less than or equals to the data of the root. The data of all the nodes in the right subtree of the root node should be greater than the data of the root. This example shows how to find height of a binary search tree.

Here is an example picture of binary search tree (BST):

Binary Search Tree

package com.java2novice.ds;

public class BstNode {

	private BstNode left;
	private BstNode right;
	private Integer data;

	public BstNode(Integer data) { = data;

	public BstNode getLeft() {
		return left;
	public void setLeft(BstNode left) {
		this.left = left;
	public BstNode getRight() {
		return right;
	public void setRight(BstNode right) {
		this.right = right;

	public Integer getData() {
		return data;

package com.java2novice.ds;

public class BinarySearchTreeImpl {

	private BstNode root;

	public boolean isEmpty() {

		return (this.root == null);

	public void insert(Integer data) {

		System.out.print("[input: "+data+"]");
		if(root == null) {
			this.root = new BstNode(data);
			System.out.println(" -> inserted: "+data);

		insertNode(this.root, data);
		System.out.print(" -> inserted: "+data);

	private BstNode insertNode(BstNode root, Integer data) {

		BstNode tmpNode = null;
		System.out.print(" ->"+root.getData());
		if(root.getData() >= data) {
			System.out.print(" [L]");
			if(root.getLeft() == null) {
				root.setLeft(new BstNode(data));
				return root.getLeft();
			} else {
				tmpNode = root.getLeft();
		} else {
			System.out.print(" [R]");
			if(root.getRight() == null) {
				root.setRight(new BstNode(data));
				return root.getRight();
			} else {
				tmpNode = root.getRight();

		return insertNode(tmpNode, data);

	public Integer findHeight(){

		return getNodeHeight(this.root);

	private Integer getNodeHeight(BstNode node) {

		if(node == null) {
			return -1;

		return Math.max(getNodeHeight(node.getLeft()), getNodeHeight(node.getRight()))+1;

	public static void main(String a[]) {

		BinarySearchTreeImpl bst = new BinarySearchTreeImpl();
		System.out.println("Height of the tree: "+bst.findHeight());

[input: 10] -> inserted: 10
[input: 20] ->10 [R] -> inserted: 20
[input: 21] ->10 [R] ->20 [R] -> inserted: 21
[input: 8] ->10 [L] -> inserted: 8
[input: 6] ->10 [L] ->8 [L] -> inserted: 6
[input: 16] ->10 [R] ->20 [L] -> inserted: 16
[input: 23] ->10 [R] ->20 [R] ->21 [R] -> inserted: 23
[input: 2] ->10 [L] ->8 [L] ->6 [L] -> inserted: 2
Height of the tree: 3
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List Of All Interview Programs:

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  3. Find out middle index where sum of both ends are equal.
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  10. Write a program to implement ArrayList.
  11. Write a program to find maximum repeated words from a file.
  12. Wrie a program to find out duplicate characters in a string.
  13. Write a program to find top two maximum numbers in a array.
  14. Write a program to sort a map by value.
  15. Write a program to find common elements between two arrays.
  16. How to swap two numbers without using temporary variable?
  17. Write a program to print fibonacci series.
  18. Write a program to find sum of each digit in the given number using recursion.
  19. Write a program to check the given number is a prime number or not?
  20. Write a program to find the given number is Armstrong number or not?
  21. Write a program to convert binary to decimal number.
  22. Write a program to check the given number is binary number or not?
  23. Write a program for Bubble Sort in java.
  24. Write a program for Insertion Sort in java.
  25. Write a program to implement hashcode and equals.
  26. How to get distinct elements from an array by avoiding duplicate elements?
  27. Write a program to get distinct word list from the given file.
  28. Write a program to get a line with max word count from the given file.
  29. Write a program to convert string to number without using Integer.parseInt() method.
  30. Write a program to find two lines with max characters in descending order.
  31. Write a program to find the sum of the first 1000 prime numbers.
  32. Find longest substring without repeating characters.
  33. Write a program to remove duplicates from sorted array.
  34. How to sort a Stack using a temporary Stack?
  35. Write a program to print all permutations of a given string.
  36. Implement Binary Search Tree (BST)
  37. Find min and max value from Binary Search Tree (BST)
  38. Find height of a Binary Search Tree (BST)
  39. Implement Binary Search Tree (BST) Level order traversal (breadth first).
  40. Implement Binary Search Tree (BST) pre-order traversal (depth first).
  41. Implement Binary Search Tree (BST) in-order traversal (depth first).
  42. Implement Binary Search Tree (BST) post-order traversal (depth first).
  43. How to check the given Binary Tree is Binary Search Tree (BST) or not?
  44. How to delete a node from Binary Search Tree (BST)?
  45. Write a program to find common integers between two sorted arrays.
Knowledge Centre
String Vs StringBuffer
We know that String is immutable object. We can not change the value of a String object once it is initiated. If we try to change the value of the existing String object then it creates new object rather than changing the value of the existing object. So incase, we are going to do more modificatios on String, then use StringBuffer. StringBuffer updates the existing objects value, rather creating new object.
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-- Harry Truman

About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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