User leakage in recommendation split
An AI built this split for a recommendation model where the same user appears in many rows. Offline metrics look great; online they don't. Explain the contamination.
Implement
split_rows_by_user(user_ids: list[str], test_user_count: int) → list[int]Examples
in
[["u1","u2","u1","u3","u2"],1]out[1,0,1,0,0]in
[["a","b","c"],2]out[1,1,0]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 19 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.
Run or narrate your approach, then ask the coach.