Python实现堆栈和队列详解

cmp830871

python实现堆栈

堆栈是一个后进先出的数据结构，其工作方式就像一堆汽车排队进去一个死胡同里面，最先进去的一定是最后出来。

我们可以设置一个类，用列表来存放栈中元素的信息，利用列表的append()和pop()方法可以实现栈的出栈pop和入栈push的操作，list.append(obj)意思是向列表添加一个对象obj,list.pop(index=-1)意思是删除指定位置的对象，默认是最后一个对象，也就是说list.pop(),是删除列表中下标最大的元素。可先将Stack类写入文件stack.py，在其它程序文件中使用from stack import Stack，然后就可以使用堆栈了。

stack.py的程序:

代码如下:

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class Stack():  

    def __init__(self,size):  

        self.size=size

        self.stack=[]

        self.top=-1

    def push(self,ele):  #入栈之前检查栈是否已满  

        if self.isfull():  

            raise exception("out of range")

        else:  

            self.stack.append(ele)

            self.top=self.top+1

    def pop(self):             # 出栈之前检查栈是否为空  

        if self.isempty():  

            raise exception("stack is empty")

        else:  

            self.top=self.top-1

            return self.stack.pop()

      

    def isfull(self):  

        return self.top+1==self.size

    def isempty(self):  

        return self.top==-1

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再写一个程序文件，stacktest.py 使用栈，内容如下:

代码如下:

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#!/usr/bin/python

from stack import Stack

s=Stack(20)

for i in range(3):  

    s.push(i)

s.pop()

# f  a; A- X/ T

print s.isempty()

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python 实现队列

队列是一种先进先出的数据类型，它的跟踪原理类似于在超市收银处排队，队列里的的第一个人首先接受服务，新的元素通过入队的方式添加到队列的末尾，而出队就是将队列的头元素删除。

　　　我们可以设置一个类，用列表来存放栈中元素的信息，利用列表的append()和pop()方法可以实现队列的入队enqueue和出队dequeue的操作，上面栈一个元素每次出去是列表的最后一个，直接用list.pop()出栈，而出队列每次是第一个，所以要用list.pop(0)出队列

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代码如下:

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class Queue():  

    def __init__(self,size):  

        self.size=size;

        self.front=-1;  

        self.rear=-1;  

        self.queue=[];

    def enqueue(self,ele):  #入队操作  

        if self.isfull():  

            raise exception("queue is full");

        else:  

            self.queue.append(ele)

            self.rear=self.rear+1

    def dequeue(self):      #出队操作  

        if self.isempty():  

            raise exception("queue is empty")

        else:  

            self.front=self.front+1

            return self.queue[self.front]

    def isfull(self):  

        return self.rear-self.front+1==self.size

    def isempty(self):  

        return self.front==self.rear

      

q=Queue(10);  

for i in range(3):  

    q.enqueue(i)

print q.dequeue()

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print q.isempty()

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