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))