func_code: def quicksort(l, p, r):
      if r <= p:
          return
      q = j = p
      while j < r:
          if l[j] <= l[r]:
              l[q], l[j] = l[j], l[q]
              q += 1
          j += 1
      l[q], l[r] = l[r], l[q]
      quicksort(l, p, q - 1)
      quicksort(l, q + 1, r)