Preorder Traversal and BST Java

PROGRAM TO CHECK IF A GIVEN ARRAY CAN REPRESENT PREORDER TRAVERSAL OF BST

import java.util.Stack;

  

class BinarySearchTree {

  

    boolean canRepresentBST(int pre[], int n) {

        // Create an empty stack

        Stack<Integer> s = new Stack<Integer>();

  

        // Initialize current root as minimum possible

        // value

        int root = Integer.MIN_VALUE;

  

        // Traverse given array

        for (int i = 0; i < n; i++) {

            // If we find a node who is on right side

            // and smaller than root, return false

            if (pre[i] < root) {

                return false;

            }

  

            // If pre[i] is in right subtree of stack top,

            // Keep removing items smaller than pre[i]

            // and make the last removed item as new

            // root.

            while (!s.empty() && s.peek() < pre[i]) {

                root = s.peek();

                s.pop();

            }

  

            // At this point either stack is empty or

            // pre[i] is smaller than root, push pre[i]

            s.push(pre[i]);

        }

        return true;

    }

  

    public static void main(String args[]) {

        BinarySearchTree bst = new BinarySearchTree();

        int[] pre1 = new int[]{40, 30, 35, 80, 100};

        int n = pre1.length;

        if (bst.canRepresentBST(pre1, n) == true) {

            System.out.println("true");

        } else {

            System.out.println("false");

        }

        int[] pre2 = new int[]{40, 30, 35, 20, 80, 100};

        int n1 = pre2.length;

        if (bst.canRepresentBST(pre2, n) == true) {

            System.out.println("true");

        } else {

            System.out.println("false");

        }

    }

}

OUTPUT:

true
false

CREDITS: https://www.geeksforgeeks.org/check-if-a-given-array-can-represent-preorder-traversal-of-binary-search-tree/