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: list.pop() raises an IndexError when called on an empty list.
The fix: Guard the pop call with a truthiness check: history.pop() if history else None
Remember: In Python, list.pop() raises IndexError on empty collections; guard before popping.
The pattern behind it: logic errors.
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