98.Validate Binary Search Tree
Description
 |
#98 | Validate Binary Search Tree | Medium | |
|---|---|---|---|---|
| Tree | MS | |||
| Given the root of a binary tree, determine if it is a valid binary search tree (BST). | ||||
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.