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98 lines
2.9 KiB
Python
98 lines
2.9 KiB
Python
"""
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Python program for Bitonic Sort.
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Note that this program works only when size of input is a power of 2.
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"""
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from __future__ import annotations
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def comp_and_swap(array: list[int], index1: int, index2: int, direction: int) -> None:
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"""Compare the value at given index1 and index2 of the array and swap them as per
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the given direction.
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The parameter direction indicates the sorting direction, ASCENDING(1) or
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DESCENDING(0); if (a[i] > a[j]) agrees with the direction, then a[i] and a[j] are
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interchanged.
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>>> arr = [12, 42, -21, 1]
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>>> comp_and_swap(arr, 1, 2, 1)
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>>> arr
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[12, -21, 42, 1]
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>>> comp_and_swap(arr, 1, 2, 0)
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>>> arr
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[12, 42, -21, 1]
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>>> comp_and_swap(arr, 0, 3, 1)
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>>> arr
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[1, 42, -21, 12]
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>>> comp_and_swap(arr, 0, 3, 0)
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>>> arr
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[12, 42, -21, 1]
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"""
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if (direction == 1 and array[index1] > array[index2]) or (
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direction == 0 and array[index1] < array[index2]
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):
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array[index1], array[index2] = array[index2], array[index1]
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def bitonic_merge(array: list[int], low: int, length: int, direction: int) -> None:
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"""
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It recursively sorts a bitonic sequence in ascending order, if direction = 1, and in
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descending if direction = 0.
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The sequence to be sorted starts at index position low, the parameter length is the
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number of elements to be sorted.
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>>> arr = [12, 42, -21, 1]
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>>> bitonic_merge(arr, 0, 4, 1)
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>>> arr
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[-21, 1, 12, 42]
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>>> bitonic_merge(arr, 0, 4, 0)
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>>> arr
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[42, 12, 1, -21]
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"""
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if length > 1:
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middle = int(length / 2)
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for i in range(low, low + middle):
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comp_and_swap(array, i, i + middle, direction)
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bitonic_merge(array, low, middle, direction)
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bitonic_merge(array, low + middle, middle, direction)
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def bitonic_sort(array: list[int], low: int, length: int, direction: int) -> None:
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"""
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This function first produces a bitonic sequence by recursively sorting its two
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halves in opposite sorting orders, and then calls bitonic_merge to make them in the
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same order.
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>>> arr = [12, 34, 92, -23, 0, -121, -167, 145]
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>>> bitonic_sort(arr, 0, 8, 1)
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>>> arr
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[-167, -121, -23, 0, 12, 34, 92, 145]
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>>> bitonic_sort(arr, 0, 8, 0)
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>>> arr
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[145, 92, 34, 12, 0, -23, -121, -167]
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"""
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if length > 1:
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middle = int(length / 2)
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bitonic_sort(array, low, middle, 1)
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bitonic_sort(array, low + middle, middle, 0)
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bitonic_merge(array, low, length, direction)
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if __name__ == "__main__":
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user_input = input("Enter numbers separated by a comma:\n").strip()
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unsorted = [int(item.strip()) for item in user_input.split(",")]
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bitonic_sort(unsorted, 0, len(unsorted), 1)
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print("\nSorted array in ascending order is: ", end="")
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print(*unsorted, sep=", ")
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bitonic_merge(unsorted, 0, len(unsorted), 0)
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print("Sorted array in descending order is: ", end="")
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print(*unsorted, sep=", ")
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