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* Pyupgrade to Python 3.9
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61 lines
1.8 KiB
Python
61 lines
1.8 KiB
Python
"""
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Slowsort is a sorting algorithm. It is of humorous nature and not useful.
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It's based on the principle of multiply and surrender,
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a tongue-in-cheek joke of divide and conquer.
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It was published in 1986 by Andrei Broder and Jorge Stolfi
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in their paper Pessimal Algorithms and Simplexity Analysis
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(a parody of optimal algorithms and complexity analysis).
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Source: https://en.wikipedia.org/wiki/Slowsort
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"""
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from __future__ import annotations
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def slowsort(sequence: list, start: int | None = None, end: int | None = None) -> None:
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"""
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Sorts sequence[start..end] (both inclusive) in-place.
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start defaults to 0 if not given.
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end defaults to len(sequence) - 1 if not given.
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It returns None.
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>>> seq = [1, 6, 2, 5, 3, 4, 4, 5]; slowsort(seq); seq
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[1, 2, 3, 4, 4, 5, 5, 6]
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>>> seq = []; slowsort(seq); seq
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[]
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>>> seq = [2]; slowsort(seq); seq
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[2]
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>>> seq = [1, 2, 3, 4]; slowsort(seq); seq
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[1, 2, 3, 4]
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>>> seq = [4, 3, 2, 1]; slowsort(seq); seq
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[1, 2, 3, 4]
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>>> seq = [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]; slowsort(seq, 2, 7); seq
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[9, 8, 2, 3, 4, 5, 6, 7, 1, 0]
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>>> seq = [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]; slowsort(seq, end = 4); seq
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[5, 6, 7, 8, 9, 4, 3, 2, 1, 0]
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>>> seq = [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]; slowsort(seq, start = 5); seq
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[9, 8, 7, 6, 5, 0, 1, 2, 3, 4]
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"""
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if start is None:
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start = 0
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if end is None:
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end = len(sequence) - 1
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if start >= end:
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return
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mid = (start + end) // 2
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slowsort(sequence, start, mid)
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slowsort(sequence, mid + 1, end)
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if sequence[end] < sequence[mid]:
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sequence[end], sequence[mid] = sequence[mid], sequence[end]
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slowsort(sequence, start, end - 1)
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if __name__ == "__main__":
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from doctest import testmod
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testmod()
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