Implement Union Find with with follow-up
Last updated: June 3, 2026
Quick Overview
Implement a LRU Cache data structure that supports insert, delete, and lookup operations in O(1) time.
Waymo
June 3, 2026117
12
1,446 solved
Implement a LRU Cache data structure that supports insert, delete, and lookup operations in O(1) time.
This coding problem is frequently asked during Phone Screen at Waymo. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Waymo expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
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
- How would you modify your solution to handle streaming input?
- What happens if the input contains duplicates?
- How would you parallelize this solution?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To implement an LRU (Least Recently Used) Cache that supports insertion, deletion, and lookup in O(1) time, we need to consider two main data structures: a hash map and a doubly linked list. The hash ...
Approach
- Data Structures: Use a hash map (
dictin Python) to store the key-value pairs and a doubly linked list to maintain the order of usage. Each node in the linked list will contain the key-value ...
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