func_code: def swap(a, i, j):
      tmp = a[i]
      a[i] = a[j]
      a[j] = tmp
  
  
  def reverse(a):
      x = 0
      y = len(a)
      z = len(a) / 2
      while x < y:
          swap(a, x, y)
          x = x + 1
          y = y - 1