Python/dynamic_programming/factorial.py
Sanders Lin f0d7879a11
fixed error in factorial.py ()
* 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>
2020-08-05 13:18:41 +02:00

28 lines
585 B
Python

# Factorial of a number using memoization
from functools import lru_cache
@lru_cache
def factorial(num: int) -> int:
"""
>>> factorial(7)
5040
>>> factorial(-1)
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:
raise ValueError("Number should not be negative.")
return 1 if num in (0, 1) else num * factorial(num - 1)
if __name__ == "__main__":
import doctest
doctest.testmod()