Apple·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Apple Data Engineer screen with a Python OOP coding problem. The setup was a bit unusual since they gave you a parent class with precomputed data and made you build on top of it, which I wasn't expecting.

Questions Asked (1)

You're given a Parent class that precomputes frequency counts of items from a list into a dictionary. Implement a method in the Child class that returns the most frequent key(s) without using Python's built-in max() function. Handle ties by returning all tied keys, and return an empty list if the input is empty.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The no-max() constraint is what made this annoying.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem constraints and edge cases (empty input, ties). Then, iterate through the frequency dictionary to find the maximum frequency without using max(), and finally collect all keys with that frequency. Discuss time and space complexity and potential optimizations.

Pro tip: Mention that you would use the precomputed dictionary from the Parent class to avoid recalculating frequencies, demonstrating awareness of inheritance and efficiency. Also, explicitly handle ties and empty input as specified, showing attention to detail.

1. Clarify requirements and edge cases

Confirm that the frequency dictionary is available from the Parent class, and discuss how to handle empty input and ties. Ask if the input list is guaranteed non-empty or if the dictionary could be empty.

2. Design the algorithm without max()

Plan to iterate through the dictionary items to find the maximum frequency value manually, then iterate again to collect all keys with that frequency. Consider using a single pass to track both max frequency and keys.

3. Implement the method in Child class

Write the method that accesses the precomputed frequency dictionary (e.g., self.freq_dict) and returns a list of most frequent keys. Ensure it returns an empty list if the dictionary is empty.

4. Analyze complexity and trade-offs

Discuss time complexity O(n) where n is number of unique items, and space complexity O(k) for storing tied keys. Mention that using a single pass can be more efficient than two passes.

5. Test with examples

Walk through test cases: empty input, single most frequent, multiple ties, all items tied. Verify that the method returns the correct list of keys.

Key Points to Mention

Avoid using max() by manually tracking the maximum frequency with a loop.
Handle ties by collecting all keys that share the maximum frequency.
Return an empty list when the frequency dictionary is empty.
Leverage the precomputed frequency dictionary from the Parent class to avoid redundant computation.
Discuss time and space complexity: O(n) time, O(k) space for k tied keys.
Consider edge cases: empty input, all items with same frequency, single item.

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