Transform array to hash map
Last updated: April 13, 2026
Quick Overview
Given an array of key-value pairs, transform it into a hash map where each key is associated with its corresponding value. The output should be a hash map that allows for efficient retrieval of values based on their keys, ensuring that if duplicate keys are present, the last value associated with that key is retained.
Two Sigma
April 13, 202635
14
940 solved
Given an array of key-value pairs, transform it into a hash map where each key is associated with its corresponding value. The output should be a hash map that allows for efficient retrieval of values based on their keys, ensuring that if duplicate keys are present, the last value associated with that key is retained.
Coding interviews at Two Sigma 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
- 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?
- What happens if the input contains duplicates?
- Can you solve this in a single pass?
- How would you parallelize this solution?
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Problem Analysis
To solve the problem of transforming an array of key-value pairs into a hash map, we should leverage the characteristics of a hash map (or dictionary in Python). The primary challenge is to ensure tha...
Approach
- Initialize an empty hash map (dictionary in Python).
- Iterate through each key-value pair in the input array.
- For each pair, insert/update the key in the hash map with its corresponding ...
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