Time: 0:00
Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).
This bug belongs to the logic errors pattern
The wrong operator, an inverted condition, a formula the right way round but backwards.
What went wrong: "A" and "a" are different characters, so the set keeps both addresses.
The fix: return len(set(e.strip().lower() for e in emails))
Remember: clean emails (strip and lowercase) as soon as they arrive.
The pattern behind it: logic errors.
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<iframe src="https://trybughunt.com/embed/9bbca31a-640f-42ba-bf7b-27bee7c5b8ad" title="Debugging challenge: A@x.com and a@x.com count as two people" width="100%" height="580" loading="lazy" style="border:1px solid #d4d4d8;border-radius:12px;max-width:760px"></iframe>
<p style="font-size:14px">Debugging challenge from <a href="https://trybughunt.com/challenges/9bbca31a-640f-42ba-bf7b-27bee7c5b8ad">TryBugHunt</a></p>