Back to Problems

Binary Search Tree Validator

Hard
binary-tree validation recursion
Problem Description

Check if a binary tree is a valid binary search tree.

Input Format
Space-separated node values in level-order (use -1 for null nodes)
Output Format
Print "VALID" if BST, "INVALID" otherwise
Constraints
1 ≤ number of nodes ≤ 1000, -1000 ≤ node values ≤ 1000
Sample Input/Output
Input: 
5 3 8 2 4 7 9
Output: 
VALID
Explanation

Tree satisfies BST property: left < root < right for all nodes

Solution Hints
  • Read carefully: Understand input/output format and constraints
  • Start simple: Think of brute force solution first, then optimize
  • Edge cases: Consider empty inputs, single elements, max constraints
  • Data structures: Choose arrays, hash maps, sets based on problem needs
  • Time complexity: Ensure your solution fits within time limits
  • Test examples: Verify logic with provided sample inputs
290
Points
2000ms
Time Limit
256MB
Memory Limit
Code Editor
Register to Submit
Register to Access Code Editor

Create a free account to solve coding problems and track your progress.

Register Now
Feedback