```
"""
Gcd of N Numbers
Reference: https://en.wikipedia.org/wiki/Greatest_common_divisor
"""
from collections import Counter
def get_factors(
number: int, factors: Counter | None = None, factor: int = 2
) -> Counter:
"""
this is a recursive function for get all factors of number
>>> get_factors(45)
Counter({3: 2, 5: 1})
>>> get_factors(2520)
Counter({2: 3, 3: 2, 5: 1, 7: 1})
>>> get_factors(23)
Counter({23: 1})
>>> get_factors(0)
Traceback (most recent call last):
...
TypeError: number must be integer and greater than zero
>>> get_factors(-1)
Traceback (most recent call last):
...
TypeError: number must be integer and greater than zero
>>> get_factors(1.5)
Traceback (most recent call last):
...
TypeError: number must be integer and greater than zero
factor can be all numbers from 2 to number that we check if number % factor == 0
if it is equal to zero, we check again with number // factor
else we increase factor by one
"""
match number:
case int(number) if number == 1:
return Counter({1: 1})
case int(num) if number > 0:
number = num
case _:
raise TypeError("number must be integer and greater than zero")
factors = factors or Counter()
if number == factor: # break condition
# all numbers are factors of itself
factors[factor] += 1
return factors
if number % factor > 0:
# if it is greater than zero
# so it is not a factor of number and we check next number
return get_factors(number, factors, factor + 1)
factors[factor] += 1
# else we update factors (that is Counter(dict-like) type) and check again
return get_factors(number // factor, factors, factor)
def get_greatest_common_divisor(*numbers: int) -> int:
"""
get gcd of n numbers:
>>> get_greatest_common_divisor(18, 45)
9
>>> get_greatest_common_divisor(23, 37)
1
>>> get_greatest_common_divisor(2520, 8350)
10
>>> get_greatest_common_divisor(-10, 20)
Traceback (most recent call last):
...
Exception: numbers must be integer and greater than zero
>>> get_greatest_common_divisor(1.5, 2)
Traceback (most recent call last):
...
Exception: numbers must be integer and greater than zero
>>> get_greatest_common_divisor(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
1
>>> get_greatest_common_divisor("1", 2, 3, 4, 5, 6, 7, 8, 9, 10)
Traceback (most recent call last):
...
Exception: numbers must be integer and greater than zero
"""
# we just need factors, not numbers itself
try:
same_factors, *factors = map(get_factors, numbers)
except TypeError as e:
raise Exception("numbers must be integer and greater than zero") from e
for factor in factors:
same_factors &= factor
# get common factor between all
# `&` return common elements with smaller value (for Counter type)
# now, same_factors is something like {2: 2, 3: 4} that means 2 * 2 * 3 * 3 * 3 * 3
mult = 1
# power each factor and multiply
# for {2: 2, 3: 4}, it is [4, 81] and then 324
for m in [factor**power for factor, power in same_factors.items()]:
mult *= m
return mult
if __name__ == "__main__":
print(get_greatest_common_divisor(18, 45)) # 9
```