Validate interval list balanced
Last updated: July 10, 2025
Quick Overview
Given a list of intervals, write a function to determine if the intervals are balanced, meaning that for every interval, there exists a corresponding interval that complements it such that the combined length of both intervals is equal. The function should take a list of intervals as input and return a boolean value indicating whether the list is balanced. An interval is represented as a pair of integers [start, end].
HubSpot
July 10, 20257
8
3,612 solved
Given a list of intervals, write a function to determine if the intervals are balanced, meaning that for every interval, there exists a corresponding interval that complements it such that the combined length of both intervals is equal. The function should take a list of intervals as input and return a boolean value indicating whether the list is balanced. An interval is represented as a pair of integers [start, end].
HubSpot uses this problem in the Take-home Project to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
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 you parallelize this solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
- Can you optimize the space complexity of your solution?
- What if the input doesn't fit in memory?
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Practice DSA ProblemsSample Answer
Problem Analysis
To determine if a list of intervals is balanced, we need to check if each interval has a corresponding complement that matches its length. This can be thought of as a two-pointer approach after sortin...
Approach
- Sort the Intervals: First, we sort the intervals based on their lengths. If an interval is represented as [start, end], its length can be calculated as
end - start. - Use Two Pointers: ...
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