leetcode-python-反转链表

第一轮解法：

1）双指针，先给定尾部为空，然后逐个出栈

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def reverseList(self, head: ListNode) -> ListNode:
        tail = None
        temp = head
        while temp:
            temp = head.next
            head.next = tail
            tail = head
            head = temp
            # tail.PrintListNode()
        return tail