Meta·Software Engineer·Onsite - Coding / Algorithms·Intermediate

Intermediate

Jun 2026

Summary

Meta SWE coding round with one algorithmic problem. Pretty straightforward simulation but the edge cases tripped me up more than I expected.

Questions Asked (1)

Given a non-negative integer array, repeatedly take the first non-zero element and subtract it from all leading elements that share the same value, continuing until all elements are zero or you hit an element strictly smaller than the one you're currently processing. Return the array at that point.

Algorithms & Data Structures

Author's notes

I read it too fast and thought it was just a prefix sum thing.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem statement and edge cases with the interviewer. Then, walk through a simple example to demonstrate understanding, and finally, propose an efficient algorithm with complexity analysis.

Pro tip: Always discuss trade-offs between different approaches (e.g., brute force vs. optimized) and mention how you would test your solution with edge cases.

1. Clarify the problem

Ask questions to ensure you understand the operation: what does 'leading elements that share the same value' mean? Confirm that you process from left to right, and that you stop when the next element is smaller.

2. Work through an example

Choose a small array (e.g., [2,2,3,1]) and manually simulate the process step by step to verify your understanding and identify patterns.

3. Design an algorithm

Think of an efficient way to simulate the process. Consider using a stack or two pointers to avoid unnecessary repeated scans.

4. Analyze complexity

Determine the time and space complexity of your approach. Aim for O(n) time and O(1) extra space if possible.

5. Test with edge cases

Consider arrays with all zeros, all same non-zero values, strictly increasing/decreasing, and large inputs to ensure correctness and efficiency.

Key Points to Mention

Understanding of the operation: subtract the first non-zero element from all leading elements with the same value until a smaller element is encountered.
Edge cases: empty array, all zeros, single element, all elements equal, strictly increasing/decreasing arrays.
Algorithm choice: simulation with a stack or two pointers to achieve linear time.
Time and space complexity: O(n) time and O(1) space if optimized.
Testing strategy: walk through examples and consider boundary conditions.
Communication: explain your thought process clearly and ask clarifying questions.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.