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Apple·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Apple SWE coding round, one algorithmic question, pretty standard but the edge cases will get you if you're not careful.

Questions Asked (1)

Q1

Given an integer array, find the contiguous subarray that has the largest product and return that product.

Algorithms & Data Structures
Author's notes

Tripped up on the negative number case for longer than I'd like to admit.

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AI HintsAI Generated

Suggested Approach

Use dynamic programming to track both the maximum and minimum product ending at each position, since a negative number can flip the sign and turn a minimum into a maximum. Iterate through the array, updating these values and the global maximum product.

Pro tip: Clearly explain why tracking the minimum product is necessary—this shows you understand the sign-flipping edge case that trips up many candidates. Also, discuss how you would handle zeros and negative numbers, and mention the time and space complexity.

1. Clarify the problem and edge cases

Ask if the array can be empty, contain zeros, or have negative numbers. Confirm that the subarray must be contiguous and non-empty.

2. Define state variables

Maintain two variables: max_prod and min_prod, representing the maximum and minimum product of a subarray ending at the current index. Also keep a global max_product.

3. Iterate and update

For each number, compute new max_prod and min_prod using the current number and the previous max_prod and min_prod. Update global max_product accordingly.

4. Handle edge cases

If the array is empty, return 0 or handle as appropriate. Zeros reset the product, so they are naturally handled by the updates.

5. Analyze complexity

State that the algorithm runs in O(n) time and O(1) space, which is optimal.

Key Points to Mention

  • Dynamic programming approach with O(n) time and O(1) space.
  • Tracking both maximum and minimum products to handle negative numbers.
  • The recurrence relations: new_max = max(num, num*max_prod, num*min_prod) and similarly for new_min.
  • Edge cases: empty array, single element, zeros, all negatives.
  • Comparison with brute force O(n^2) or O(n^3) approaches to highlight efficiency.
  • Potential follow-up: return the subarray itself, not just the product.

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