Python/sorts/shell_sort.py

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"""
This is a pure Python implementation of the shell sort algorithm
For doctests run following command:
python -m doctest -v shell_sort.py
or
python3 -m doctest -v shell_sort.py
For manual testing run:
python shell_sort.py
"""
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def shell_sort(collection):
"""Pure implementation of shell sort algorithm in Python
:param collection: Some mutable ordered collection with heterogeneous
comparable items inside
:return: the same collection ordered by ascending
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>>> shell_sort([0, 5, 3, 2, 2])
[0, 2, 2, 3, 5]
>>> shell_sort([])
[]
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>>> shell_sort([-2, -5, -45])
[-45, -5, -2]
"""
# Marcin Ciura's gap sequence
gaps = [701, 301, 132, 57, 23, 10, 4, 1]
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for gap in gaps:
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for i in range(gap, len(collection)):
j = i
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while j >= gap and collection[j] < collection[j - gap]:
collection[j], collection[j - gap] = collection[j - gap], collection[j]
j -= gap
return collection
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if __name__ == "__main__":
user_input = input("Enter numbers separated by a comma:\n").strip()
unsorted = [int(item) for item in user_input.split(",")]
print(shell_sort(unsorted))