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In place of calculating the factorial several times we can run a loop k times to calculate the combination #10051

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Merged
merged 4 commits into from
Oct 8, 2023
Merged

In place of calculating the factorial several times we can run a loop k times to calculate the combination #10051

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79c7e38
In place of calculating the factorial several times we can run a loop…
SubhranShu2332 Oct 7, 2023
ec2491c
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Oct 7, 2023
a91ff20
Update maths/combinations.py
tianyizheng02 Oct 8, 2023
62ba059
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Oct 8, 2023
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7 changes: 5 additions & 2 deletions maths/combinations.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
"""
https://en.wikipedia.org/wiki/Combination
"""
from math import factorial


def combinations(n: int, k: int) -> int:
Expand Down Expand Up @@ -35,7 +34,11 @@ def combinations(n: int, k: int) -> int:
# to calculate a factorial of a negative number, which is not possible
if n < k or k < 0:
raise ValueError("Please enter positive integers for n and k where n >= k")
return factorial(n) // (factorial(k) * factorial(n - k))
res = 1
for i in range(k):
res = res * (n - i)
res = res // (i + 1)
return res


if __name__ == "__main__":
Expand Down