用Python体现单链表的增删改查

在Python中，我们可以使用类（Class）来实现单链表的数据结构。单链表包含节点（Node），每个节点通常包含两个部分：数据（data）和指向下一个节点的引用（next）。这里是一个简单的单链表类的实现，包括增删改查操作：

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


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

    # 插入元素到链表头部
    def insert_at_start(self, data):
        new_node = Node(data)
        new_node.next = self.head
        self.head = new_node

    # 在特定位置插入元素
    def insert_at_position(self, position, data):
        if position <= 0:
            print("Invalid position")
            return
        if position == 1:
            self.insert_at_start(data)
        else:
            current = self.head
            for _ in range(position - 2):
                if not current:
                    break
                current = current.next
            if not current:
                print("Position out of bounds")
                return
            new_node = Node(data)
            new_node.next = current.next
            current.next = new_node

    # 删除节点
    def delete(self, key):
        if not self.head:
            print("List is empty")
            return
        if self.head.data == key:
            self.head = self.head.next
            return
        current = self.head
        while current.next and current.next.data != key:
            current = current.next
        if not current.next:
            print(f"{key} not found in the list")
        else:
            current.next = current.next.next

    # 查询节点是否存在
    def search(self, key):
        current = self.head
        while current:
            if current.data == key:
                return True
            current = current.next
        return False

    # 打印链表
    def display(self):
        elements = []
        current = self.head
        while current:
            elements.append(current.data)
            current = current.next
        print("Elements in the linked list:", elements)


# 示例
linked_list = LinkedList()
linked_list.insert_at_start(5)
linked_list.insert_at_position(2, 7)
linked_list.display()  # 输出: Elements in the linked list: [5, 7]
print(linked_list.search(7))  # 输出: True
linked_list.delete(7)
linked_list.display()