Implement Hash Map with O(1) space
Last updated: March 29, 2026
Quick Overview
Implement a hash map data structure that supports the basic operations of inserting, deleting, and retrieving key-value pairs with O(1) time complexity for each operation. Your implementation should handle collisions using a suitable method, such as chaining or open addressing. The hash map should be able to store and manage a set of integer keys and their associated string values, returning null for non-existent keys.
HashiCorp
March 29, 202649
13
565 solved
Implement a hash map data structure that supports the basic operations of inserting, deleting, and retrieving key-value pairs with O(1) time complexity for each operation. Your implementation should handle collisions using a suitable method, such as chaining or open addressing. The hash map should be able to store and manage a set of integer keys and their associated string values, returning null for non-existent keys.
Coding interviews at HashiCorp 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
- 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 if the input doesn't fit in memory?
- How would you parallelize this solution?
- How would you test this solution thoroughly?
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Practice DSA ProblemsSample Answer
Problem Analysis
To implement a hash map with O(1) time complexity for operations like insertion, deletion, and retrieval, we need to utilize a hash function to map keys to indices in an array. The challenge lies in h...
Approach
- Hash Function: Create a simple hash function that takes an integer key and returns an index based on the array size. For example,
index = key % array_size. - Array Initialization: Init...
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