Time: 0:00
Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).
This bug belongs to the infinite loops pattern
The tab freezes, nothing prints, and the loop condition never becomes false.
What went wrong: i += 1 is inside the if. When a pass finds no pair, i never moves, so the outer loop repeats forever.
The fix: move i += 1 to after the inner loop, at the same indentation as j = i + 1.
Remember: in Python, indentation decides which loop a line belongs to.
The pattern behind it: infinite loops.
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<iframe src="https://trybughunt.com/embed/2339cbce-30d9-484f-8fcb-e27eedb2f908" title="Debugging challenge: Counting pairs freezes when a pass finds none" 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/2339cbce-30d9-484f-8fcb-e27eedb2f908">TryBugHunt</a></p>