无头结点单循环链表实现约瑟夫，写出代码

无头节点单循环链表实现约瑟夫环问题（Josephus Problem），通常涉及在一个环形数组中按照给定步长删除元素。下面是一个简单的Python示例，使用了链表的概念：

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

def josephus_list(head, step):
    if not head or step <= 1:
        return None

    current = head
    count = 0
    while True:
        count += 1
        # 删除当前节点
        current = current.next
        if current == head:
            break
        if count % step == 0:
            continue
    return current

# 示例：创建一个单循环链表，然后应用约瑟夫环算法
head = Node(1)
head.next = Node(2)
head.next.next = Node(3)
head.next.next.next = Node(4)

deleted_node = josephus_list(head, 3)  # step=3

if deleted_node:
    print("删除后的链表：")
    node = head
    while node is not None:
        print(node.value, end=" -> ")
        node = node.next
else:
    print("所有节点都被删除，链表为空。")