random_pivot_quick_sort.py

"""
Picks the random index as the pivot
"""
import random


def partition(A, left_index, right_index):
    pivot = A[left_index]
    i = left_index + 1
    for j in range(left_index + 1, right_index):
        if A[j] < pivot:
            A[j], A[i] = A[i], A[j]
            i += 1
    A[left_index], A[i - 1] = A[i - 1], A[left_index]
    return i - 1


def quick_sort_random(A, left, right):
    if left < right:
        pivot = random.randint(left, right - 1)
        A[pivot], A[left] = (
            A[left],
            A[pivot],
        )  # switches the pivot with the left most bound
        pivot_index = partition(A, left, right)
        quick_sort_random(
            A, left, pivot_index
        )  # recursive quicksort to the left of the pivot point
        quick_sort_random(
            A, pivot_index + 1, right
        )  # recursive quicksort to the right of the pivot point


def main():
    user_input = input("Enter numbers separated by a comma:\n").strip()
    arr = [int(item) for item in user_input.split(",")]

    quick_sort_random(arr, 0, len(arr))

    print(arr)


if __name__ == "__main__":
    main()