Transform array to hash map
Last updated: January 5, 2026
Quick Overview
Given an array of key-value pairs, transform it into a hash map where each key corresponds to its respective value. The output should be a hash map that efficiently stores and retrieves the values based on the provided keys. Ensure that the solution handles duplicate keys by retaining the last value associated with each key.
Shopify
January 5, 202641
12
389 solved
Given an array of key-value pairs, transform it into a hash map where each key corresponds to its respective value. The output should be a hash map that efficiently stores and retrieves the values based on the provided keys. Ensure that the solution handles duplicate keys by retaining the last value associated with each key.
This coding problem is frequently asked during Phone Screen at Shopify. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Shopify expects candidates to write production-quality code, not just solve the puzzle.
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
- What happens if the input contains duplicates?
- How would your solution change if the input was sorted?
- What if the input doesn't fit in memory?
- What is the worst-case input for your solution?
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Problem Analysis
This problem can be effectively solved using a hash map (or dictionary in Python) due to its key-value association nature. The requirement to handle duplicate keys by retaining the last value suggests...
Approach
- Initialize an empty hash map.
- Iterate through the array of key-value pairs:
- For each pair, extract the key and value.
- Insert the key and value into the hash map. If the key already exi...
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