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
        if head is None:
            return head 
        stack = []
        while head:
            stack.append(head)
            head = head.next
        head = stack.pop()
        cur = head
        while stack:
            cur.next = stack.pop()
            cur = cur.next
        cur.next = None
        return head



  

栈的先进后出是天然的反转，需要注意的是反转之后，要断开原链表的连接，即最后一个的next要设置为None