Find longest subsequence in interval list
Last updated: February 1, 2026
Quick Overview
Given a list of intervals, find the longest subsequence of non-overlapping intervals. The input will be a list of intervals represented by pairs of integers, where each pair denotes the start and end of an interval. The output should be the length of the longest subsequence of intervals that do not overlap.
Roblox
February 1, 20265
11
2,088 solved
Given a list of intervals, find the longest subsequence of non-overlapping intervals. The input will be a list of intervals represented by pairs of integers, where each pair denotes the start and end of an interval. The output should be the length of the longest subsequence of intervals that do not overlap.
Coding interviews at Roblox 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
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?
- How would you test this solution thoroughly?
- How would your solution change if the input was sorted?
- How would you parallelize this solution?
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Problem Analysis
The problem is about finding the longest subsequence of non-overlapping intervals. This situation can be modeled using a greedy algorithm approach, where we aim to select intervals that leave the maxi...
Approach
- Sort the intervals: Start by sorting the list of intervals based on their end times. This allows us to prioritize intervals that leave the most space for future selections. For example, given i...
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