Validate matrix valid BST
Last updated: August 31, 2025
Quick Overview
Given a binary search tree (BST) represented as a 2D matrix, write a function to validate whether the matrix correctly represents a valid BST. The function should return true if the matrix adheres to the properties of a BST, where for each node, all values in the left subtree are less than the node's value and all values in the right subtree are greater. The input will be a 2D array of integers, and the output should be a boolean indicating the validity of the BST.
Expedia
August 31, 2025138
14
3,003 solved
Given a binary search tree (BST) represented as a 2D matrix, write a function to validate whether the matrix correctly represents a valid BST. The function should return true if the matrix adheres to the properties of a BST, where for each node, all values in the left subtree are less than the node's value and all values in the right subtree are greater. The input will be a 2D array of integers, and the output should be a boolean indicating the validity of the BST.
This coding problem is frequently asked during Onsite at Expedia. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Expedia expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
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
- Can you optimize the space complexity of your solution?
- What is the worst-case input for your solution?
- How would your solution change if the input was sorted?
- How would you test this solution thoroughly?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to validate whether a 2D matrix correctly represents a binary search tree (BST). The properties of a BST dictate that for any given node, all values in the left subtree must be...
Approach
We will use a recursive function to validate each node's value against its valid range. The function will take three parameters: the value of the current node, the lower bound, and the upper bound. Fo...
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