Validate interval list balanced
Last updated: February 9, 2026
Quick Overview
Determine if a given linked list satisfies the valid BST property.
Square/Block
Coding & Algorithms
Software Engineer
Square/Block
February 9, 2026Software Engineer
Onsite
Coding & Algorithms
Medium
7
3
1,004 solved
Determine if a given linked list satisfies the valid BST property.
Coding interviews at Square/Block focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
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
Binary search and divide and conquer
Time and space complexity analysis
Sorting and searching
Dynamic programming and memoization
Tree structures and recursion
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 solve this in a single pass?
- What if the input doesn't fit in memory?
- What is the worst-case input for your solution?
- How would you modify your solution to handle streaming input?
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Problem Analysis
To determine if a given linked list satisfies the valid BST property, we need to recognize that a valid BST requires that for each node, all values in the left subtree must be less than the node's val...
Approach
- Start with a recursive function that takes a node, a minimum value (lower bound), and a maximum value (upper bound).
- For each node:
- Check if its value is within the allowed range (between...
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