# -*- 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==None or pHead.next==None:
return pHead
pre = None
while pHead:
next = pHead.next
pHead.next = pre
pre = pHead
pHead = next
return pre