Validate binary tree valid BST
Last updated: January 7, 2026
Quick Overview
Determine if a given binary tree satisfies the valid BST property.
HRT
January 7, 2026339
13
1,457 solved
Determine if a given binary tree satisfies the valid BST property.
This coding problem is frequently asked during Phone Screen at HRT. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. HRT expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would your solution change if the input was sorted?
- How would you parallelize this solution?
- What happens if the input contains duplicates?
Sharpen Your Skills on Codemia
Practice similar problems with our interactive workspace, get AI feedback, and track your progress.
Practice DSA ProblemsSample Answer
Problem Analysis
To determine if a binary tree is a valid Binary Search Tree (BST), we need to ensure that for every node, all values in its left subtree are less than the node's value, and all values in its right sub...
Approach
We can implement a depth-first search (DFS) approach recursively. The algorithm follows these steps:
- Start with the root node and initialize the range as negative infinity to positive infinity.
- ...
Submit Your Answer
