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Apple·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Apple data engineer screen, one coding question, pretty standard stuff. The problem itself wasn't hard but I always second-guess my Roman numeral logic mid-interview.

Questions Asked (1)

Q1

Write a function to convert a Roman numeral string to an integer.

Algorithms & Data Structures
Author's notes

I've done this problem before so I wasn't totally lost, but I fumbled explaining the subtractive case logic out loud.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the Roman numeral rules, especially the subtractive notation (e.g., IV = 4, IX = 9). Then propose a solution that iterates through the string, comparing each character's value with the next to decide whether to add or subtract. Finally, discuss time and space complexity and consider edge cases.

Pro tip: At Apple, interviewers value clean, efficient code and clear communication. Before coding, walk through a few examples (e.g., 'MCMXCIV' = 1994) to demonstrate your understanding and catch off-by-one errors early.

1. Clarify rules and constraints

Ask about input validity (e.g., will the string always be a valid Roman numeral?) and the range of values (1 to 3999). Confirm the subtractive notation rules.

2. Outline the algorithm

Explain that you'll map each symbol to its value, then iterate left to right. If the current value is less than the next, subtract it; otherwise, add it.

3. Code the solution

Write clean code with a hash map for symbol values and a loop that handles the comparison. Use a single pass for O(n) time and O(1) space.

4. Test with examples

Walk through test cases like 'III' (3), 'IV' (4), 'IX' (9), 'LVIII' (58), and 'MCMXCIV' (1994) to verify correctness.

5. Analyze complexity and edge cases

State that time complexity is O(n) and space is O(1). Mention edge cases like empty string, single character, and invalid input handling.

Key Points to Mention

  • Subtractive notation: when a smaller value precedes a larger one, it's subtracted (e.g., IV, IX, XL, XC, CD, CM).
  • Use a hash map to store symbol-to-value mappings for O(1) lookups.
  • Single-pass iteration comparing current and next character values.
  • Time complexity O(n) and space complexity O(1).
  • Handling invalid input gracefully (e.g., return 0 or throw an exception).
  • Testing with a variety of cases, including the maximum value 3999 (MMMCMXCIX).

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