This program checks whether a Binary tree is a BST or not, can someone explain me the working of recursive return statement in the function isBSTUtil
public class BinaryTree {
Node root; boolean isBST() { return isBSTUtil(root, Integer.MIN_VALUE, Integer.MAX_VALUE); } boolean isBSTUtil(Node node, int min, int max) { if (node == null) return true; if (node.data < min || node.data > max) return false; return (isBSTUtil(node.left, min, node.data-1) && isBSTUtil(node.right, node.data+1, max)); } public static void main(String args[]) { BinaryTree tree = new BinaryTree(); tree.root = new Node(4); tree.root.left = new Node(2); tree.root.right = new Node(5); tree.root.left.left = new Node(1); tree.root.left.right = new Node(3); if (tree.isBST()) System.out.println("IS BST"); else System.out.println("Not a BST"); }
} class Node { int data; Node left, right;
public Node(int item) { data = item; left = right = null; }
}