``````"""
Python program for Bitonic Sort.

Note that this program works only when size of input is a power of 2.
"""
from __future__ import annotations

def comp_and_swap(array: list[int], index1: int, index2: int, direction: int) -> None:
"""Compare the value at given index1 and index2 of the array and swap them as per
the given direction.

The parameter direction indicates the sorting direction, ASCENDING(1) or
DESCENDING(0); if (a[i] > a[j]) agrees with the direction, then a[i] and a[j] are
interchanged.

>>> arr = [12, 42, -21, 1]
>>> comp_and_swap(arr, 1, 2, 1)
>>> print(arr)
[12, -21, 42, 1]

>>> comp_and_swap(arr, 1, 2, 0)
>>> print(arr)
[12, 42, -21, 1]

>>> comp_and_swap(arr, 0, 3, 1)
>>> print(arr)
[1, 42, -21, 12]

>>> comp_and_swap(arr, 0, 3, 0)
>>> print(arr)
[12, 42, -21, 1]
"""
if (direction == 1 and array[index1] > array[index2]) or (
direction == 0 and array[index1] < array[index2]
):
array[index1], array[index2] = array[index2], array[index1]

def bitonic_merge(array: list[int], low: int, length: int, direction: int) -> None:
"""
It recursively sorts a bitonic sequence in ascending order, if direction = 1, and in
descending if direction = 0.
The sequence to be sorted starts at index position low, the parameter length is the
number of elements to be sorted.

>>> arr = [12, 42, -21, 1]
>>> bitonic_merge(arr, 0, 4, 1)
>>> print(arr)
[-21, 1, 12, 42]

>>> bitonic_merge(arr, 0, 4, 0)
>>> print(arr)
[42, 12, 1, -21]
"""
if length > 1:
middle = int(length / 2)
for i in range(low, low + middle):
comp_and_swap(array, i, i + middle, direction)
bitonic_merge(array, low, middle, direction)
bitonic_merge(array, low + middle, middle, direction)

def bitonic_sort(array: list[int], low: int, length: int, direction: int) -> None:
"""
This function first produces a bitonic sequence by recursively sorting its two
halves in opposite sorting orders, and then calls bitonic_merge to make them in the
same order.

>>> arr = [12, 34, 92, -23, 0, -121, -167, 145]
>>> bitonic_sort(arr, 0, 8, 1)
>>> arr
[-167, -121, -23, 0, 12, 34, 92, 145]

>>> bitonic_sort(arr, 0, 8, 0)
>>> arr
[145, 92, 34, 12, 0, -23, -121, -167]
"""
if length > 1:
middle = int(length / 2)
bitonic_sort(array, low, middle, 1)
bitonic_sort(array, low + middle, middle, 0)
bitonic_merge(array, low, length, direction)

if __name__ == "__main__":
user_input = input("Enter numbers separated by a comma:\n").strip()
unsorted = [int(item.strip()) for item in user_input.split(",")]

bitonic_sort(unsorted, 0, len(unsorted), 1)
print("\nSorted array in ascending order is: ", end="")
print(*unsorted, sep=", ")

bitonic_merge(unsorted, 0, len(unsorted), 0)
print("Sorted array in descending order is: ", end="")
print(*unsorted, sep=", ")
``````

#### Bitonic Sort  