python扩展数据结构—栈和队列

栈：只在表尾进行插入删除的线性表。

class Stack():       

    def __init__(self):

        self.stack = []

   

    def empty(self):

        return self.stack == []

   

    def top(self):

        if self.empty():

            return None

        else:

            return self.stack[-1]

       

    def pop(self):

        if self.empty():

            return None

        else:

            return self.stack.pop(-1)

       

    def push(self,obj):

        self.stack.append(obj)

       

    def length(self):

        return len( self.stack)

队列：在一端进行插入另一端进行删除的线性表。

class Queue():

    def __init__(self):

        self.data = []

    def empty(self):

        return self.data == []

    def length(self):

        return len( self.data)

    def head(self):

        if not self.empty():

            return self.data[0]

        else:

            return None

    def enQueue(self,element):

        self.data.append(element)

    def deQueue(self):

        if not self.empty():

            return self.data.pop(0)

        else:

            return None

    def __str__(self):

        return str( self.data)