LeetCode Challenge #98. Validate Binary Search Tree

Day 95 of 100 Days LeetCode Challenge

LeetCode Challenge #98. Validate Binary Search Tree

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

A valid 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.

Example 1:

Input: root = [2,1,3]
Output: true

Example 2:

Input: root = [5,1,4,null,null,3,6]
Output: false
Explanation: The root node's value is 5 but its right child's value is 4.

Constraints:

The number of nodes in the tree is in the range [1, 10⁴].
-2³¹ <= Node.val <= 2³¹ - 1

Video Solution

Java Solution

				
					class Solution {
    public boolean isValidBST(TreeNode root) {
        return helper(root, Long.MIN_VALUE , Long.MAX_VALUE);
    }

    public boolean helper(TreeNode root , long min , long max ){
        if(root==null){
            return true ;
        }

        if(root.val<=min || root.val>=max){
            return false ;
        }

        boolean leftAns = helper(root.left , min , root.val);
        boolean rightAns = helper(root.right , root.val , max );
        return leftAns && rightAns ;
    }
}

Day 95 of 100 Days LeetCode Challenge

LeetCode Challenge #98. Validate Binary Search Tree

Video Solution

Java Solution

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