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

Intermediate

May 2026

Summary

Meta SWE coding round with one algorithmic problem that looks deceptively simple but has a few edge cases that'll trip you up if you're not careful. The simulation logic is the kind of thing you either see immediately or spend ten minutes redrawing on a whiteboard.

Questions Asked (1)

Given an integer array, repeatedly scan from left to right: record the first non-zero value you encounter, then for each subsequent element, subtract that recorded value if the element is greater than or equal to it, or stop the pass if it's smaller. After each full pass, add the recorded value to a result list. Keep going until the whole array is zeroed out. Return the sum of the result list.

Algorithms & Data Structures

Author's notes

I spent the first few minutes just trying to understand what 'stop the pass' actually meant.

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AI HintsAI Generated

Suggested Approach

First, restate the problem in your own words to confirm understanding, then walk through a small example to illustrate the process. Next, identify the core operation (repeatedly subtracting the minimum non-zero value) and propose an efficient algorithm, such as sorting or using a min-heap, to avoid simulating each pass. Finally, analyze time and space complexity and discuss potential edge cases.

Pro tip: Mention that the sum of recorded values equals the sum of all distinct non-zero values in the array, which can be computed in O(n) time without simulating passes. This demonstrates insight and can lead to a more efficient solution.

1. Clarify and Restate

Restate the problem in your own words and confirm any ambiguities, such as whether the array can contain negative numbers or zeros.

2. Walk Through Example

Choose a small array (e.g., [1,3,2]) and manually simulate the process to ensure you understand the mechanics and can explain it clearly.

3. Identify Core Operation

Recognize that each pass subtracts the current minimum non-zero value from all elements greater than or equal to it, effectively removing that minimum from the array.

4. Design Efficient Algorithm

Propose an approach that avoids full simulation, such as sorting the array and summing distinct non-zero values, or using a min-heap to repeatedly extract the minimum.

5. Analyze Complexity and Edge Cases

Discuss time and space complexity of your solution, and consider edge cases like empty array, all zeros, or large input sizes.

Key Points to Mention

The sum of recorded values equals the sum of all distinct non-zero elements in the array.
Sorting the array allows you to compute the sum in O(n log n) time by iterating and adding only when the value changes.
A min-heap can also be used to extract the minimum repeatedly, but sorting is simpler and often more efficient.
The problem can be solved in O(n) time if you use a hash set to track distinct non-zero values, but sorting is acceptable for most interviews.
Edge cases: empty array, array with all zeros, array with negative numbers (if allowed), and large arrays.
Communication: explain your thought process clearly, start with a brute-force simulation, then optimize.

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