Code RoomFilter missing return statement
MediumPrep Room Coding #4007

Filter missing return statement

Vibe & agenticAlgorithms & data structuresMid–Senior~14 min

An AI assistant wrote this JavaScript to deduplicate an array of order objects by their `id`, keeping the first occurrence:

It returns the right length on a small test where all ids differ. What's the bug, and when does it bite?

Implement
dedupe_ids(order_ids: list[str]) → list[str]
Examples
in[["a","b","a","c"]]out["a","b","c"]
in[["a","a","a"]]out["a"]
in[["x","y","z"]]out["x","y","z"]
What a strong answer looks like

Treat the AI’s output as a draft to verify, not an answer to trust. Name the specific flaw and the input that triggers it, say how you’d catch it (tests, edge cases, reading critically), and how you’d re-prompt or decompose to get it right.

0:00 of about 14 min

Vibe & agentic: describe the solution in plain language (or narrate it) and the coach grades your approach.

Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.