Transform matrix to hash map

Last updated: May 3, 2026

Quick Overview

Convert the given array to sorted result following the specified rules.

Airbnb
Coding & Algorithms
Software Engineer
Airbnb
May 3, 2026
Software Engineer
Phone Screen
Coding & Algorithms
Hard

29

8

1,340 solved


Convert the given array to sorted result following the specified rules.

This coding problem is frequently asked during Phone Screen at Airbnb. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Airbnb 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
Tree structures and recursion
Dynamic programming and memoization
Data structure selection and trade-offs
Hash maps and frequency counting
Time and space complexity analysis
How to Approach This
  1. Clarify input constraints and edge cases before writing code.
  2. Walk through your approach verbally and confirm with the interviewer before coding.
  3. Start with a brute force solution, then optimize. Mention time and space complexity.
  4. Test your solution with examples, including edge cases like empty input or duplicates.
  5. Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
  • How would your solution change if the input was sorted?
  • What happens if the input contains duplicates?
  • How would you parallelize this solution?
Sharpen Your Skills on Codemia

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Sample Answer
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