Looked straightforward and then I started coding and realized I had no clean way to handle the thousands/millions/billions groupings without repeating myself.
Break the problem into chunks of three digits (thousands, millions, billions) and convert each chunk to words using a helper function. Then concatenate the chunks with appropriate scale words (Thousand, Million, Billion) and handle edge cases like zero and multiples of ten.
Pro tip: Mention that you would clarify the expected output format (e.g., spaces, hyphens, 'and') and discuss trade-offs between a recursive vs. iterative approach, showing attention to detail and scalability.
Ask about the exact format (e.g., 'One Million' vs 'one million'), handling of zero, and whether to include 'and' or hyphens. Confirm the range and that the input is nonnegative.
Create a function that converts any number from 0 to 999 into words using arrays for ones, teens, and tens, and handling hundreds with 'Hundred'.
Iteratively extract the last three digits, convert them using the helper, and prepend the appropriate scale word (Thousand, Million, Billion).
Concatenate the chunk representations with spaces, ensuring no extra spaces and handling the special case of zero.
Verify with inputs like 0, 100, 1000, 1000000, and 2147483647. Mention time complexity O(n) where n is number of digits, and space O(1) for fixed-size arrays.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.