剑指offer-15.反转链表-Python

反转链表

题目描述

输入一个链表，反转链表后，输出新链表的表头。

记录

三个指针合作：

举例：

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    # 返回ListNode
    def ReverseList(self, pHead):
        # write code here
        if pHead is None or pHead.next is None:
            return pHead
        pre = None
        while pHead:
        	#tmp暂存下一个节点
            tmp = pHead.next
            pHead.next = pre
            pre = pHead
            pHead = tmp
        return pre