Implement Priority Queue with with follow-up
Last updated: November 21, 2025
Quick Overview
Implement a LRU Cache data structure that supports push, pop, and peek operations in O(1) time.
Elastic
November 21, 202531
6
1,298 solved
Implement a LRU Cache data structure that supports push, pop, and peek operations in O(1) time.
Coding interviews at Elastic 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
- What is the worst-case input for your solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you test this solution thoroughly?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to implement an LRU (Least Recently Used) cache that supports push, pop, and peek operations in O(1) time complexity. The LRU cache must store key-value pairs and evict t...
Approach
- Data Structures: Use a hash map to store key-value pairs where keys are the cache keys and values are the nodes in a doubly linked list. The doubly linked list will maintain the order of access...
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