#binary?tree?node
class?Node:
????father?=?None
????left?=?None
????right?=?None
????key?=?0
????def?__init__（selfkeyfather?=?Noneleft?=?Noneright?=?None）:
????????super（）.__init__（）
????????self.father?=?father
????????self.left?=?left
????????self.right?=?right
????????self.key?=?key
#a?kind?of?simulation?of?a?real?procedure
class?Procedure:
????__context?=?{‘steps‘:[]}
????__next?=?0
????def?__init__（selfcontextsteps）:
????????super（）.__init__（）
????????context[‘steps‘]?=?steps
????????self.__context?=?context

????def?nextStep（self）:
????????tem?=?self.__context[‘steps‘][self.__next]（self.__context）?#do?as?a?function
????????self.__next?=?self.__next?+?1
????????return?tem

????def?isComplete（self）:
????????if?len（self.__context[‘steps‘]）?????????????return?True
????????else:
????????????return?False

#a?stack?used?to?store?doing?procedures
class?ProcedureStack:
????__allProcedures?=?[]
????def?push（self?procedure）:
????????self.__allProcedures.append（procedure）
????def?pop（self）:
????????self.__allProcedures.pop（-1）
????def?top（self）:
????????return?self.__allProcedures[-1]
????def?isEmpty（self）:
????????if?len（self.__allProcedures）?<=?0:
????????????return?True
????????else:
????????????return?False

#trditional?recursion?（used?to?test?binary?tree）
def?PrintRecursion（root）:
????if?root.left?==?None:
????????print（root.key）
????????return
????PrintRecursion（root.left）
????print（root.key）
????PrintRecursion（root.right）

#step?function1?in?recursion?simulation
def?