leetcode 206 python 反转链表

传送门

题目要求

反转一个单链表。

示例:
输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

思路一

遍历给定链表，摘下节点放到新链表，新链表从后向前构造

→_→ talk is cheap, show me the code

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if not head:
            return None
        new = None
        while head:
            p = head
            head = head.next
            p.next = new
            new = p
        return new