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Update 3n_plus_1.py (#7966)

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* Update 3n_plus_1.py

1. Minor issue with ValueError message: Given integer should be positive, not greater than 1, as 1 is allowed.
2. += calls underlying list extend method which might be slower. Calling apend seems more appropriate.

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Sanders Lin 2022-11-06 17:35:40 +08:00 committed by GitHub
parent 7f1a5521f4
commit 51708530b6
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1 changed files with 3 additions and 3 deletions
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maths/3n_plus_1.py
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@ -11,15 +11,15 @@ def n31(a: int) -> tuple[list[int], int]:
if not isinstance(a, int):
raise TypeError(f"Must be int, not {type(a).__name__}")
if a < 1:
raise ValueError(f"Given integer must be greater than 1, not {a}")
raise ValueError(f"Given integer must be positive, not {a}")
path = [a]
while a != 1:
if a % 2 == 0:
a = a // 2
a //= 2
else:
a = 3 * a + 1
path += [a]
path.append(a)
return path, len(path)