leetcode-206 反转链表

递归反转链表，还有迭代？？ 代码待补充

# 自己写的
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def reverseList(self, head: ListNode) -> ListNode:
        if not head:
            return None
        self.reverse_li = None
        node = self.reverse(head)
        # 注意这里有个坑 一定要把尾巴断干净
        node.next = None
        return self.reverse_li
    
    def reverse(self, node):
        
        if not node.next:
            self.reverse_li = node
            return node
        next_node = self.reverse(node.next)
        next_node.next = node
        return node