A reluctant sorting algorithm

slowsort.py

# https://www.mipmip.org/tidbits/pasa.pdf
# Pessimal Algorithmsand Simplexity Analysis. Broder, Stolfi
def helper(A, i, j):
  # in-place sort the subarray A[i],...,A[j] using multiply-and-surrender
  if i >= j:
    return
  m = (i+j)//2
  helper(A, i, m)
  helper(A, m+1, j)
  if A[m] > A[j]:
    A[m],A[j] = A[j],A[m]
  helper(A, i, j-1)
  
# start recursion and return the sorted array
def slowsort(A):
  helper(A, 0, len(A)-1)
  return A