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Merged
realDuYuanChao
merged 4 commits into
TheAlgorithms:master
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Rolv-Apneseth:change-combinations.py
Oct 26, 2020
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Original file line number | Diff line number | Diff line change |
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@@ -1,19 +1,58 @@ | ||
""" | ||
https://en.wikipedia.org/wiki/Combination | ||
""" | ||
from math import factorial | ||
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def combinations(n, k): | ||
def combinations(n: int, k: int) -> int: | ||
""" | ||
Returns the number of different combinations of k length which can | ||
be made from n values, where n >= k. | ||
|
||
Examples: | ||
>>> combinations(10,5) | ||
252 | ||
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>>> combinations(6,3) | ||
20 | ||
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>>> combinations(20,5) | ||
15504 | ||
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>>> combinations(52, 5) | ||
2598960 | ||
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>>> combinations(0, 0) | ||
1 | ||
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>>> combinations(-4, -5) | ||
... | ||
Traceback (most recent call last): | ||
ValueError: Please enter positive integers for n and k where n >= k | ||
""" | ||
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# If either of the conditions are true, the function is being asked | ||
# 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 int(factorial(n) / ((factorial(k)) * (factorial(n - k)))) | ||
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if __name__ == "__main__": | ||
from doctest import testmod | ||
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testmod() | ||
print( | ||
"\nThe number of five-card hands possible from a standard", | ||
f"fifty-two card deck is: {combinations(52, 5)}", | ||
) | ||
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||
print( | ||
"\nIf a class of 40 students must be arranged into groups of", | ||
f"4 for group projects, there are {combinations(40, 4)} ways", | ||
"to arrange them.\n", | ||
) | ||
|
||
print( | ||
"If 10 teams are competing in a Formula One race, there", | ||
f"are {combinations(10, 3)} ways that first, second and", | ||
"third place can be awarded.\n", | ||
) |
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