题解 | 反转链表

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
#
# @param head ListNode类
# @return ListNode类
#
class Solution:
    def ReverseList(self, head: ListNode) -> ListNode:
        # write code here
        p = None
        while head:
            head.next, p, head = p, head, head.next
        return p