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:
        #这里需要注意，从head节点就开始反转，如果pre=head,pre=head.next,头节点的next指针没有变，而正常应该指向空
        pre = None
        cur = head
        while cur != None:
            tmp = cur.next
            cur.next = pre
            pre = cur
            cur = tmp
        return pre