python实现快速排序 --算法导论

import random
def partition(A, p, r):
    x = A[r]
    i = p - 1
    for j in range(p, r):
        if A[j] <= x:
            i = i + 1
            A[i], A[j] = A[j], A[i]
    A[i + 1], A[r] = A[r], A[i + 1]
    return i + 1

def randomized_partition(A, p, r):
    i = random.randint(p, r)
    A[r], A[i] = A[i], A[r]
    return partition(A, p, r)
def randomized_quicksort(A, p, r):
    if p < r:
        q =randomized_partition(A, p, r)
        randomized_quicksort(A, p, q - 1)
        randomized_quicksort(A, q + 1, r)
        return A
A = [13, 19, 9, 5, 12, 8, 7, 4, 21, 2, 6, 11]#需要排序数组 
print(randomized_quicksort(A, 0, len(A) - 1))