X Interview Questions
The coding and system-design questions asked in X interviews - with worked solutions, in-browser code execution, and active-recall review. 5 questions.
- Valid Parentheses
Stack-walk a bracket string to validate it, then localize the first error, then find the longest valid substring (LC 32).
Practicalmedium35m2mo
+12 - Find Duplicate Files(premium)
Group identical files by content. Stream-hash to keep memory bounded, then add size pre-filtering and an opt-in symlink/min-size policy.
Practicalmedium45m2mo
+4 - Encode and Decode Strings(premium)
Serialize a list of arbitrary strings into a single string and parse it back. Any character is allowed in the strings, including the delimiters - length-prefix framing is the only safe answer.
Practicaleasy25m2mo+3 - Time-Based Key-Value Store(premium)
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.
Practicalmedium35m2mo
+9 - Authentication Manager - TTL(premium)
LeetCode 1797. Tokens issued with a fixed TTL; renew before expiry to extend; count live tokens at time t. Later phases push the count to amortized O(1) and add thread safety.
Practicalmedium30m2mo