Two Pointers on interval list
Last updated: April 26, 2026
Quick Overview
Given a list of intervals, implement a function using the two pointers technique to merge overlapping intervals and return a new list of non-overlapping intervals. The input will be an array of intervals, where each interval is represented as a pair of integers [start, end]. The output should be a list of merged intervals in ascending order based on their start times.
Dropbox
April 26, 20263
15
3,703 solved
Given a list of intervals, implement a function using the two pointers technique to merge overlapping intervals and return a new list of non-overlapping intervals. The input will be an array of intervals, where each interval is represented as a pair of integers [start, end]. The output should be a list of merged intervals in ascending order based on their start times.
Dropbox 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
- 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
- What happens if the input contains duplicates?
- How would you test this solution thoroughly?
- What is the worst-case input for your solution?
- What if the input doesn't fit in memory?
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
The problem of merging overlapping intervals can be effectively solved using the two pointers technique. Here, we can view the intervals as a sorted list of pairs, where each pair indicates the st...
Approach
- Sort the intervals: First, we sort the intervals based on the start time. For example, given intervals
[[1,3],[2,6],[8,10],[15,18]], after sorting, we have[[1,3],[2,6],[8,10],[15,18]]. 2....
Submit Your Answer
