回答編集履歴

  def quick_sort(a, first, last):

  if first < last:

  pivot = a[last]

  for j in range(first, last):

  if a[j] <= pivot:

  i += 1

  a[i], a[last] = a[last], a[i]

  quick_sort(a, first, i-1)

  quick_sort(a, i+1, last)