Microsoft·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Jun 2026

Summary

Microsoft SWE coding round, one question the whole time. Pretty focused session, no small talk, just straight into the problem.

Questions Asked (1)

Given an integer array with positive and negative numbers, find the sum of the longest contiguous subarray made up entirely of positive numbers. If there's a tie in length, return the highest sum. Return 0 if no positive numbers exist. Walk through the algorithm, its complexity, and write working code.

Algorithms & Data Structures

Author's notes

Took me a minute to get the edge cases straight in my head.

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AI HintsAI Generated

Suggested Approach

Clarify the problem and edge cases, then propose a single-pass linear scan that tracks the current positive run's length and sum, updating the best result when a longer run is found or when lengths tie but the sum is higher. Walk through a small example, state O(n) time and O(1) space, and then write clean, tested code.

Pro tip: Microsoft interviewers value clean, bug-free code and clear communication; before coding, restate the tie-breaking rule and edge cases (all negatives, zeros, single element) to show thoroughness, and after coding, offer to test with a few cases.

1. Clarify requirements and edge cases

Confirm that 'positive' means strictly greater than zero, and that zeros break the contiguous positive run. Discuss edge cases: empty array, all negatives, all positives, and ties in length.

2. Outline the algorithm

Explain a single-pass approach: iterate through the array, maintain current run length and sum, and update the best result when the current run is longer, or equal in length but has a higher sum. Reset the run when a non-positive number is encountered.

3. Analyze complexity

State that the algorithm runs in O(n) time and uses O(1) extra space, which is optimal since every element must be examined at least once.

4. Write the code

Implement the algorithm in a clean, readable function with meaningful variable names. Include comments for clarity and handle the edge case where no positive numbers exist by returning 0.

5. Test and validate

Walk through a few test cases, including the provided example, edge cases, and a tie-breaking scenario, to demonstrate correctness and catch off-by-one errors.

Key Points to Mention

Single-pass O(n) time and O(1) space solution
Handling of zeros and negative numbers as breakers of contiguous positive runs
Tie-breaking rule: when lengths are equal, choose the subarray with the higher sum
Edge cases: empty array, no positive numbers (return 0), all positives, and ties
Clear variable naming and code readability
Testing with examples to verify correctness

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