302 队列的实现2 #

1. 数据出队的实现
2. 队列的实现

数据出队的实现 #

队列数据的出队比进队相比，首先需要判断队列是否为空
数据出队时需要首先将出队的元素保存下来用于返回，然后更新头部指针，最后需要将出队节点的next置空

def poll(self):
    if(self.front == None):
        print("the queue is mepty now!!!")
    else:
        temp = self.front
        self.front = self.front.next
        temp.next = None
        return temp.data

队列的实现 #

队列类的整体实现如下，包含了数据进队、出队的基本方法offer, poll

class Node:
    def __init__(self, data):
        self.data = data  # 用于存储数据
        self.next = None  # 用于指向下一数据

class Queue:
    def __init__(self):
        self.front = None  # 头部指针
        self.rear = None  # 尾部指针

    def offer(self, data):
        new_node = Node(data)  # 构造一个节点数据
        if(self.rear == None):
            self.front = new_node
        else:
            self.rear.next = new_node
        self.rear = new_node
        new_node.next = None

    def poll(self):
        if(self.front == None):
            print("the queue is mepty now!!!")
        else:
            temp = self.front
            self.front = self.front.next
            temp.next = None
            return temp.data

    def __str__(self):  # 重载__str__()函数用于,用于print()打印
        if((self.front == None) & (self.rear == None)):
            return("This is a queue structure\n" +
                   "the queue is empty now!!!")
        else:
            return("This is a queue structure\n" +
                   "the rear data is "+str(self.rear.data)+"\n"
                   "the front data is "+str(self.front.data))

myqueue1 = Queue()  # 实例化一个队列结构
print(myqueue1)
myqueue1.offer(3)  # 进队列
myqueue1.offer([1, 2])  # 进队列
print(myqueue1)
poll_value = myqueue1.poll()
print(poll_value)
print(myqueue1)

小结 #

习题 #

1. 给上述的栈结构加入一个实例变量length，用来存贮队的长度
2. 详细描述一下队头出队、队尾进队的细节，并绘制其过程