Validate interval list symmetric
Last updated: August 9, 2025
Quick Overview
Given a list of intervals, determine if the list is symmetric, meaning that for every interval [a, b], there exists a corresponding interval [c, d] such that a + d = b + c. The input will be an array of intervals, and the output should be a boolean value indicating whether the list is symmetric or not.
Plaid
August 9, 2025109
7
1,644 solved
Given a list of intervals, determine if the list is symmetric, meaning that for every interval [a, b], there exists a corresponding interval [c, d] such that a + d = b + c. The input will be an array of intervals, and the output should be a boolean value indicating whether the list is symmetric or not.
Plaid uses this problem in the Technical Screen 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
- Can you solve this iteratively instead of recursively (or vice versa)?
- Can you optimize the space complexity of your solution?
- How would you modify your solution to handle streaming input?
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Practice DSA ProblemsSample Answer
Problem Analysis
To determine if the list of intervals is symmetric, we need to understand the relationship between the intervals. The symmetry condition states that for every interval [a, b], there should exist a cor...
Approach
- Transform Intervals: For each interval [a, b], compute the value
s = a + band store the intervals in a list of tuples with their sums. - Sort Intervals: Sort the list of tuples based o...
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