Practice Validate Binary Search Tree

Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.

Medium#98

LeetCode Problem

Validate Binary Search Tree

Tree Depth-First Search Binary Search Tree Binary Tree

Problem Statement

Determine whether a binary tree is a strict binary search tree. Every value anywhere in a node's left subtree must be smaller than that node; every value in its right subtree must be larger. Apply the same condition recursively. Duplicate values are invalid, even when the immediate parent comparison would appear correct. Practice approach: Carry an exclusive lower and upper bound into each subtree. A node must lie inside both bounds. Alternatively, an inorder traversal must be strictly increasing. Visit each node once: O(n) time and O(h) traversal space.

Source: Validate Binary Search Tree on LeetCode. Use the original task for its coding environment and submissions.

Examples

# Example 1

Input

root = [2,1,3]

Output

true

# Example 2

Input

root = [5,1,4,null,null,3,6]

Output

false

Constraints

The tree contains between 1 and 10000 nodes.

-(2^31) <= Node.val <= 2^31 - 1

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