Time: 0:00
Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).
This bug belongs to the scope and closure bugs pattern
Every callback reports the last value, a counter never increments, UnboundLocalError on a variable you can see.
What went wrong: new Array(count).fill([]) copies the exact same array reference into every slot. Modifying bucket 0 mutates all buckets.
The fix: Use Array.from() with a factory function to create independent arrays: Array.from({ length: count }, () => [])
Remember: In JavaScript, array.fill() with an object or array copies the reference, sharing state across all elements.
The pattern behind it: scope and closure bugs.
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<iframe src="https://trybughunt.com/embed/6e57332d-6ce8-4061-b814-2380d0aebcd8" title="Debugging challenge: Array fill with empty array shares same sublist instance" 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/6e57332d-6ce8-4061-b814-2380d0aebcd8">TryBugHunt</a></p>