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Code RoomString truncation with multibyte characters
HardPrep Room Coding #4006

String truncation with multibyte characters

Vibe & agenticAlgorithms & data structuresSenior~17 min

You asked an AI assistant for a Go function that truncates a user bio to 20 characters with an ellipsis, for a profile preview. It produced:

It looks right on ASCII bios. What input corrupts the output, and what's the real fix?

Implement
preview_by_runes(bio: str, max_runes: int) → str
Examples
in["hello",20]out"hello"
in["abcdefghij",5]out"abcde…"
in["😀😀😀😀😀😀",3]out"😀😀😀…"
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 17 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.