Started with the slice reversal approach because it's clean and readable.
Start by clarifying the problem and edge cases, then propose a two-pointer approach that skips non-alphanumeric characters and compares characters case-insensitively. Discuss time and space complexity, and mention alternative approaches like filtering and reversing, highlighting trade-offs.
Pro tip: At Apple, emphasize clean, efficient code and consider Unicode and locale-specific cases; mention that in-place two-pointer avoids extra space, which is often valued in ML engineering for large-scale data processing.
Ask about input constraints, definition of alphanumeric (ASCII vs Unicode), and expected behavior for empty strings or strings with only non-alphanumeric characters.
Explain using left and right pointers, moving inward while skipping non-alphanumeric characters and comparing lowercased characters.
State O(n) time and O(1) space for two-pointer; compare with O(n) space for filtering and reversing, noting when each is preferable.
Write clean code with helper functions for alphanumeric check and lowercasing, then walk through test cases like 'A man, a plan, a canal: Panama' and edge cases.
Mention how palindrome checking relates to sequence validation in ML, and how handling Unicode is important for global products.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.