Python/maths/aliquot_sum.py
Kenneth P a29a2a3a06
Added file aliquot_sum.py (#1985)
* Added file aliquot_sum.py containing a function to find theo

* Added parameter type info to aliquot_sum.py

* Update maths/aliquot_sum.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update maths/aliquot_sum.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Updated code to raise ValueErrors if input is bad

* Fixed logical operators

* Removed unnecessary import

* Updated aliquot_sum.py

* fixed formatting

* fixed documentation

Co-authored-by: Christian Clauss <cclauss@me.com>
2020-05-15 08:06:51 +02:00

47 lines
1.4 KiB
Python

def aliquot_sum(input_num: int) -> int:
"""
Finds the aliquot sum of an input integer, where the
aliquot sum of a number n is defined as the sum of all
natural numbers less than n that divide n evenly. For
example, the aliquot sum of 15 is 1 + 3 + 5 = 9. This is
a simple O(n) implementation.
@param input_num: a positive integer whose aliquot sum is to be found
@return: the aliquot sum of input_num, if input_num is positive.
Otherwise, raise a ValueError
Wikipedia Explanation: https://en.wikipedia.org/wiki/Aliquot_sum
>>> aliquot_sum(15)
9
>>> aliquot_sum(6)
6
>>> aliquot_sum(-1)
Traceback (most recent call last):
...
ValueError: Input must be positive
>>> aliquot_sum(0)
Traceback (most recent call last):
...
ValueError: Input must be positive
>>> aliquot_sum(1.6)
Traceback (most recent call last):
...
ValueError: Input must be an integer
>>> aliquot_sum(12)
16
>>> aliquot_sum(1)
0
>>> aliquot_sum(19)
1
"""
if not isinstance(input_num, int):
raise ValueError("Input must be an integer")
if input_num <= 0:
raise ValueError("Input must be positive")
return sum(divisor for divisor in range(1, input_num) if input_num % divisor == 0)
if __name__ == "__main__":
import doctest
doctest.testmod()