使用pyhton语言写一个双向链表

首先，我们需要定义一个节点类，包括数据域和两个指针域，一个向前指针和一个向后指针：

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

然后我们再定义一个双向链表类，包括头指针、尾指针和节点数量，以及各种操作的方法：

class DoublyLinkedList:
    def __init__(self):
        self.head = None
        self.tail = None
        self.count = 0

    def append(self, data):
        """在尾部添加节点"""
        new_node = Node(data)
        if self.head is None:
            self.head = new_node
            self.tail = new_node
        else:
            new_node.prev = self.tail
            self.tail.next = new_node
            self.tail = new_node
        self.count += 1

    def delete(self, node):
        """删除节点"""
        if self.head is None or node is None:
            return
        if self.head == node:
            self.head = node.next
        if self.tail == node:
            self.tail = node.prev
        if node.prev is not None:
            node.prev.next = node.next
        if node.next is not None:
            node.next.prev = node.prev
        self.count -= 1

    def find(self, data):
        """查找节点"""
        current = self.head
        while current is not None:
            if current.data == data:
                return current
            current = current.next
        return None

    def print_list(self):
        """打印链表"""
        current = self.head
        while current is not None:
            print(current.data, end=' ')
            current = current.next
        print()

这样就可以使用双向链表了，例如：

dl_list = DoublyLinkedList()
dl_list.append(1)
dl_list.append(2)
dl_list.append(3)
dl_list.append(4)
dl_list.print_list()  # 输出 1 2 3 4
node = dl_list.find(3)
dl_list.delete(