Transform matrix to sorted array
Last updated: August 19, 2025
Quick Overview
Given a 2D matrix of integers, transform the matrix into a sorted one-dimensional array in ascending order. The output should be a single array containing all the elements of the matrix sorted from the smallest to the largest. Ensure that the solution handles matrices of varying dimensions and is efficient in terms of time and space complexity.
Postmates
August 19, 202597
15
2,437 solved
Given a 2D matrix of integers, transform the matrix into a sorted one-dimensional array in ascending order. The output should be a single array containing all the elements of the matrix sorted from the smallest to the largest. Ensure that the solution handles matrices of varying dimensions and is efficient in terms of time and space complexity.
This coding problem is frequently asked during Phone Screen at Postmates. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Postmates 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
- How would you modify your solution to handle streaming input?
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would your solution change if the input was sorted?
- What happens if the input contains duplicates?
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Practice DSA ProblemsSample Answer
Problem Analysis
To transform a 2D matrix into a sorted one-dimensional array, we can recognize that this problem fundamentally requires us to gather all elements from the matrix and then sort them. The most direct pa...
Approach
- Initialize an empty list to hold all elements from the matrix.
- Loop through each row of the matrix:
- For each row, loop through its elements and append them to the list.
- Once all elements...
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