使用链表实现队列数据结构的Python程序

当需要使用链表实现队列数据结构时，定义一种方法将元素添加到链表中（入队操作），并且定义一种方法删除链表中的元素（出队操作）。

下面是这个操作的演示。-

例子

class Node:
    def __init__(self, data):
    self.data = data
    self.next = None

class Queue_structure:
    def __init__(self):
        self.head = None
        self.last = None

    def enqueue_operation(self, data):
        if self.last is None:
            self.head = Node(data)
            self.last = self.head
        else:
            self.last.next = Node(data)
            self.last = self.last.next

    def dequeue_operation(self):
        if self.head is None:
            return None
        else:
            val_returned = self.head.data
            self.head = self.head.next
            return val_returned

my_instance = Queue_structure()
while True:
    print('enqueue <value>')
    print('dequeue')
    print('quit')
    my_input = input('What operation would you like to perform ? ').split()

    operation = my_input[0].strip().lower()
    if operation == 'enqueue':
        my_instance.enqueue_operation(int(my_input[1]))
    elif operation == 'dequeue':
        dequeued = my_instance.dequeue_operation()
        if dequeued is None:
            print('The queue is empty.')
        else:
            print('The deleted element is : ', int(dequeued))
    elif operation == 'quit':
        break

输出

enqueue <value>
dequeue
quit
What operation would you like to perform ? enqueue 45
enqueue <value>
dequeue
quit
What operation would you like to perform ? enqueue 12
enqueue <value>
dequeue
quit
What operation would you like to perform ? dequeue
The deleted element is : 45
enqueue <value>
dequeue
quit
What operation would you like to perform ? quit