Greedy on interval list
Last updated: July 31, 2025
Quick Overview
Given a list of intervals, each defined by a start and end time, implement a greedy algorithm to select the maximum number of non-overlapping intervals. Your function should take an array of intervals as input and return a list of selected intervals that do not overlap, ensuring optimal selection based on the earliest finishing time.
Plaid
July 31, 202513
15
628 solved
Given a list of intervals, each defined by a start and end time, implement a greedy algorithm to select the maximum number of non-overlapping intervals. Your function should take an array of intervals as input and return a list of selected intervals that do not overlap, ensuring optimal selection based on the earliest finishing time.
Coding interviews at Plaid 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
- 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
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you modify your solution to handle streaming input?
- What happens if the input contains duplicates?
- What is the worst-case input for your solution?
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Problem Analysis
This problem is a classic example of the Greedy Algorithm approach, particularly suitable for selecting non-overlapping intervals. The reason the greedy approach is applicable here is due to the p...
Approach
- Sort the Intervals: First, sort the input list of intervals based on their end times. For example, given intervals
[(1, 3), (2, 4), (3, 5)], after sorting, they remain as `[(1, 3), (2, 4), (3...
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