func_code: def quicksort(a, start, end):
      if end - start < 1:
          return
      i = k = start
      while i <= end:
          if a[i] <= a[end]:
              a[i], a[k] = a[k], a[i]
              k = k + 1
          i = i + 1
      quicksort(a, start, k - 2)
      quicksort(a, j, end)