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"""

This is a pure Python implementation of the merge sort algorithm

For doctests run following command:

python -m doctest -v merge_sort.py

or

python3 -m doctest -v merge_sort.py

For manual testing run:

python merge_sort.py

"""

def merge_sort(collection: list) -> list:

"""Pure implementation of the merge sort algorithm in Python

:param collection: some mutable ordered collection with heterogeneous

comparable items inside

:return: the same collection ordered by ascending

Examples:

>>> merge_sort([0, 5, 3, 2, 2])

[0, 2, 2, 3, 5]

>>> merge_sort([])

[]

>>> merge_sort([-2, -5, -45])

[-45, -5, -2]

"""

def merge(left: list, right: list) -> list:

"""merge left and right

:param left: left collection

:param right: right collection

:return: merge result

"""

def _merge():

while left and right:

yield (left if left[0] <= right[0] else right).pop(0)

yield from left

yield from right

return list(_merge())

if len(collection) <= 1:

return collection

mid = len(collection) // 2

return merge(merge_sort(collection[:mid]), merge_sort(collection[mid:]))

if __name__ == "__main__":

import doctest

doctest.testmod()

user_input = input("Enter numbers separated by a comma:\n").strip()

unsorted = [int(item) for item in user_input.split(",")]

print(*merge_sort(unsorted), sep=",")