Leetcode: Validate Binary Search Tree

Given a binary tree, determine if it is a valid binary search tree (BST).

Assume a BST is defined as follows:

• The left subtree of a node contains only nodes with keys less than the node's key.
• The right subtree of a node contains only nodes with keys greater than the node's key.
• Both the left and right subtrees must also be binary search trees.

Solution

public class Solution {
    public boolean isValidBST(TreeNode root) {
        return isValidBST(root, Integer.MIN_VALUE, Integer.MAX_VALUE);
    }
    public boolean isValidBST(TreeNode root, int min, int max) 
    {
        if(root == null)
            return true;
        if(root.val>=max || root.val<=min)
            return false;
        return isValidBST(root.left, min, root.val) && isValidBST(root.right, root.val, max);
    }
}