Implement Hash Map with O(1) space
Last updated: June 2, 2026
Quick Overview
Implement a LRU Cache data structure that supports insert, delete, and lookup operations in O(1) time.
Shopify
June 2, 2026204
5
725 solved
Implement a LRU Cache data structure that supports insert, delete, and lookup operations in O(1) time.
Shopify uses this problem in the Onsite 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
- Can you solve this in a single pass?
- What happens if the input contains duplicates?
- Can you solve this iteratively instead of recursively (or vice versa)?
- Can you optimize the space complexity of your solution?
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
This problem requires us to implement an LRU (Least Recently Used) Cache which efficiently supports insert, delete, and lookup operations in O(1) time complexity. The pattern that applies here is the ...
Approach
- Data Structures: Use a Hash Map to store key-value pairs where the key is the cache key and the value is a reference to a node in the Doubly Linked List. The nodes in the Doubly Linked List wil...
Submit Your Answer
