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

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

    def append(self, data):
        new_node = Node(data)
        if not self.head:
            self.head = new_node
            return
        last_node = self.head
        while last_node.next:
            last_node = last_node.next
        last_node.next = new_node

    def display(self):
        current = self.head
        while current:
            print(current.data, end=' -> ')
            current = current.next
        print('None')

# 創(chuàng)建鏈表
my_list = LinkedList()
my_list.append(1)
my_list.append(2)
my_list.append(3)

# 展示鏈表
my_list.display()

class LinkedList:
    # ...（上面的代碼）

    def insert_after(self, prev_node, data):
        if not prev_node:
            print("Previous node is not in the list.")
            return
        new_node = Node(data)
        new_node.next = prev_node.next
        prev_node.next = new_node

    def delete_node(self, key):
        current = self.head
        if current and current.data == key:
            self.head = current.next
            current = None
            return
        prev = None
        while current and current.data != key:
            prev = current
            current = current.next
        if current is None:
            return
        prev.next = current.next
        current = None

# 創(chuàng)建鏈表
my_list = LinkedList()
my_list.append(1)
my_list.append(3)
my_list.append(4)
# 插入節(jié)點
node = my_list.head.next
my_list.insert_after(node, 2)
# 刪除節(jié)點
my_list.delete_node(3)
# 展示鏈表
my_list.display()