Implement Hash Map with in-place
Last updated: August 30, 2025
Quick Overview
Implement a hash map data structure that supports in-place get and put operations with average time complexity of O(1). Your implementation should handle collisions using chaining or open addressing and should be able to resize dynamically when the load factor exceeds a certain threshold. The input will consist of key-value pairs for insertion, and the output should be the value associated with a given key for retrieval.
xAI
August 30, 2025124
11
3,578 solved
Implement a hash map data structure that supports in-place get and put operations with average time complexity of O(1). Your implementation should handle collisions using chaining or open addressing and should be able to resize dynamically when the load factor exceeds a certain threshold. The input will consist of key-value pairs for insertion, and the output should be the value associated with a given key for retrieval.
This coding problem is frequently asked during Phone Screen at xAI. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. xAI expects candidates to write production-quality code, not just solve the puzzle.
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
- What if the input doesn't fit in memory?
- How would you parallelize this solution?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To implement a hash map with in-place operations, we need to ensure that both get and put methods have an average time complexity of O(1). The most suitable pattern here is the hashing techniq...
Approach
- Initialization: Start with a fixed-size array of buckets (e.g., size 10) and a threshold for resizing (e.g., 0.7).
- Hash Function: Create a function to calculate the hash value of the k...
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