MediumCoding

Validate IP Address

Asked at

Salesforce

1Give yourself 5 minutes

2Answer out loud, not in your head

3Then compare with the answer below

Stuck? Show a way to structure it+

01Reject malformed delimiter counts first.
02Validate each IPv4 or IPv6 segment independently.
03Check leading-zero, length, range, and character rules.
04Return the matching family or neither.

Reference answer

For IPv4, split into exactly four nonempty dot-separated parts; each must contain digits only, have no leading zero unless it is 0, and parse to 0 through 255. For IPv6, split into exactly eight nonempty colon-separated groups; each has length 1 through 4 and only hexadecimal characters. Do not accept compressed IPv6 unless the specification explicitly does. The scan is O(n) time and O(1) extra space apart from split storage. Parsing with a permissive library often accepts formats the interview problem forbids.

Then expect these follow-ups

How would you support IPv6 :: compression?
Tests: protocol rules
How would you validate without allocating split arrays?
Tests: stream parsing

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