DFS on interval list
Last updated: February 19, 2026
Quick Overview
Given a list of intervals, implement a Depth-First Search (DFS) algorithm to find all possible combinations of non-overlapping intervals. Your function should take a list of intervals as input and return a list of lists, where each sublist contains intervals that do not overlap. Ensure that your solution efficiently handles edge cases, such as empty input or fully overlapping intervals.
Twitter/X
February 19, 202610
13
559 solved
Given a list of intervals, implement a Depth-First Search (DFS) algorithm to find all possible combinations of non-overlapping intervals. Your function should take a list of intervals as input and return a list of lists, where each sublist contains intervals that do not overlap. Ensure that your solution efficiently handles edge cases, such as empty input or fully overlapping intervals.
This coding problem is frequently asked during Technical Screen at Twitter/X. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Twitter/X expects candidates to write production-quality code, not just solve the puzzle.
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
- What happens if the input contains duplicates?
- How would you parallelize this solution?
- Can you optimize the space complexity of your solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
In this problem, we are tasked with finding all combinations of non-overlapping intervals from a given list. The core pattern here is Depth-First Search (DFS), which is suitable because we need to exp...
Approach
- Sort the Intervals: Start by sorting the list of intervals based on their start times. This helps in quickly identifying overlaps. For example, given intervals
[(1, 3), (2, 4), (3, 5)], sorti...
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