分别展示双向列表和循环列表是怎么实现的

双向链表是一种数据结构，每个节点包含两个指针，一个指向前一个节点，一个指向后一个节点。常见的双向链表操作包括插入、删除和遍历。

以下是一个简单的双向链表的实现：

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

class DoublyLinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        new_node = Node(data)
        if self.head is None:
            self.head = new_node
        else:
            current = self.head
            while current.next:
                current = current.next
            current.next = new_node
            new_node.prev = current

    def delete(self, data):
        current = self.head
        while current:
            if current.data == data:
                if current.prev:
                    current.prev.next = current.next
                    if current.next:
                        current.next.prev = current.prev
                else:
                    self.head = current.next
                    if current.next:
                        current.next.prev = None
                return
            current = current.next

    def print_list(self):
        current = self.head
        while current:
            print(current.data)
            current = current.next

循环链表是一种特殊类型的链表，它的最后一个节点指向第一个节点，形成一个循环。常见的循环链表操作包括插入、删除和遍历。

以下是一个简单的循环链表的实现：

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

class CircularLinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        new_node = Node(data)
        if self.head is None:
            self.head = new_node
            new_node.next = self.head
        else:
            current = self.head
            while current.next != self.head:
                current = current.next
            current.next = new_node
            new_node.next = self.head

    def delete(self, data):
        if self.head is None:
            return
        elif self.head.data == data:
            current = self.head
            while current.next != self.head:
                current = current.next
            current.next = self.head.next
            self.head = self.head.next
        else:
            current = self.head
            prev = None
            while current.next != self.head:
                prev = current
                current = current.next
                if current.data == data:
                    prev.next = current.next
                    return

    def print_list(self):
        current = self.head
        while current:
            print(current.data)
            current = current.next
            if current == self.head:
                break