First clarify the exact requirements: are we validating a single address, parsing multiple addresses, or extracting addresses from a string? Then choose a robust parsing strategy, such as splitting on dots and validating each octet, or using a regex, while handling edge cases like leading zeros, empty parts, and out-of-range values. Finally, discuss time/space complexity and potential optimizations.
Pro tip: Mention that leading zeros are often disallowed in strict IPv4 validation (e.g., '192.168.01.1' is invalid) and that you should confirm this with the interviewer. Also, consider using a state machine or finite automaton for a more scalable solution if the input is a stream.
Ask whether the task is validation, parsing, or extraction, and confirm edge cases like leading zeros, empty octets, and whether to support IPv4-mapped IPv6 addresses.
Decide between splitting on dots and validating each part, or using a regular expression. Consider readability, performance, and maintainability.
For each octet, check that it is numeric, has no leading zeros (unless it's '0'), and is between 0 and 255. Ensure there are exactly four octets.
Test with inputs like '0.0.0.0', '255.255.255.255', '192.168.1.1', '192.168.1', '192.168.1.256', '192.168.01.1', and empty strings.
State that the solution runs in O(n) time and O(1) space for a single address. Discuss potential optimizations or alternative approaches if needed.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.