Is This a Binary Search Tree? HackerRank Solution

Is This a Binary Search Tree? HackerRank Solution
Source : https://www.hackerrank.com/challenges/is-binary-search-tree

For the purposes of this challenge, we define a binary tree to be a binary search tree with the following ordering requirements:

• The value of every node in a node's left subtree is less than the data value of that node.
• The value of every node in a node's right subtree is greater than the data value of that node.

Given the root node of a binary tree, can you determine if it's also a binary search tree?

Complete the function in your editor below, which has parameter: a pointer to the root of a binary tree. It must return a boolean denoting whether or not the binary tree is a binary search tree. You may have to write one or more helper functions to complete this challenge.

Input Format

You are not responsible for reading any input from stdin. Hidden code stubs will assemble a binary tree and pass its root node to your function as an argument.

Constraints

Output Format

You are not responsible for printing any output to stdout. Your function must return true if the tree is a binary search tree; otherwise, it must return false. Hidden code stubs will print this result as a Yes or No answer on a new line.

Sample Input

Sample Output

No

Source : https://www.hackerrank.com/challenges/is-binary-search-tree

Solution

	// Karthikalapati.blogspot.com
	/*
	The Node class is defined as follows:
	class Node {
	int data;
	Node left;
	Node right;
	}
	*/
	boolean checkBST(Node root) {
	return checkBST(root, 0, 10000);
	}
	boolean checkBST(Node node, int min, int max) {
	if (node == null) {
	return true;
	} else if (node.data < min || node.data > max) { // we assume BST cannot have duplicate values
	return false;
	} else {
	return checkBST(node.left, min, node.data - 1) && checkBST(node.right, node.data + 1, max);
	}
	}