X Coding Interview Questions

Five escalating takes on one bracket string: validate it, point editor squigglies at it, mine the longest valid substring, repair a broken file, and validate with a corruptable wildcard.

Group identical files by content, keeping memory bounded while scanning, then add size pre-filtering and an opt-in symlink/min-size policy.

Serialize a list of arbitrary strings into a single string and parse it back. Any character is allowed in the strings, including the delimiters - the format must round-trip them all.

A key-value store with timestamped writes. Read at time t returns the latest value written at or before t; later phases add arbitrary-order inserts and range queries.

Tokens issued with a fixed TTL; renew before expiry to extend; count live tokens at time t. Later phases make the count efficient under many issued tokens and add thread safety.