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 ListNode:
    def __init__(self,x,next=None):
        self.val=x
        self.next=None

class Solution:
    def ReverseList(self , head: ListNode) -> ListNode:
        # write code here
        if not head:
            return None    
        pre=None
        head1=head
        while head1:
            temp=head1.next
            head1.next=pre
            pre=head1
            head1=temp
        return pre