# -*- coding:utf-8 -*-
class GrayCode:
  def getGray(self, n):
    # write code here
    global maxn
    maxn = n
    return GrayCode.getGrace(self, ['0', '1'], 1)
  def getGrace(self, list_grace, n):
    global maxn
    if n >= maxn:
      return list_grace
    list_befor, list_after = [], []
    for i in xrange(len(list_grace)):
      list_befor.append('0' + list_grace[i])
      list_after.append('1' + list_grace[-(i + 1)])
    return GrayCode.getGrace(self, list_befor + list_after, n + 1)
gary = GrayCode()
print "测试结果："
print gary.getGray(3)