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fixed error in factorial.py (#1888)

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* Update factorial.py

* updating DIRECTORY.md

* Update dynamic_programming/factorial.py

* Update factorial.py

Co-authored-by: mateuszz0000 <mtszzwdzk@gmail.com>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>
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Sanders Lin 2020-08-05 19:18:41 +08:00 committed by GitHub
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commit f0d7879a11
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1 changed files with 11 additions and 22 deletions
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dynamic_programming/factorial.py
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@ -1,36 +1,25 @@
# Factorial of a number using memoization
result = [-1] * 10
result[0] = result[1] = 1
from functools import lru_cache
def factorial(num):
@lru_cache
def factorial(num: int) -> int:
"""
>>> factorial(7)
5040
>>> factorial(-1)
'Number should not be negative.'
>>> [factorial(i) for i in range(5)]
[1, 1, 2, 6, 24]
Traceback (most recent call last):
...
ValueError: Number should not be negative.
>>> [factorial(i) for i in range(10)]
[1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880]
"""
if num < 0:
return "Number should not be negative."
if result[num] != -1:
return result[num]
else:
result[num] = num * factorial(num - 1)
# uncomment the following to see how recalculations are avoided
# print(result)
return result[num]
raise ValueError("Number should not be negative.")
return 1 if num in (0, 1) else num * factorial(num - 1)
# factorial of num
# uncomment the following to see how recalculations are avoided
# result=[-1]*10
# result[0]=result[1]=1
# print(factorial(5))
# print(factorial(3))
# print(factorial(7))
if __name__ == "__main__":
import doctest