Issue checking if binary tree is also binary search tree

Question

I\'m trying to solve this problem but I\'m having some troubles:

In a binary search tree (BST):

• The data value of every node in a

Answer 1

A BST is defined as:

-The left subtree of a node always contains nodes with values less than that of the node. - The right subtree of a node always contains nodes with values greater than that of the node. -Both left and right sub trees are also valid BSTs.

    class Solution {
        public boolean isValidBST(TreeNode root) {
            return helper (root,Integer.MIN_VALUE,Integer.MAX_VALUE);
        }
        public boolean helper(TreeNode root,long low,long high){
            if (root==null){
                return true;
            }
            if (root.valhigh){
                return false;
            }
            return (helper(root.left,low,root.val-1) && 
    helper(root.right,root.val+1,high));
        }
    }