To prove safety Offer 24

 1 # -*- coding:utf-8 -*-
 2 # class ListNode:
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.next = None
 6 class Solution:
 7     # 返回ListNode
 8     def ReverseList(self, pHead):
 9         if pHead == None:
10             return None
11         head = pHead
12         nextnode = pHead.next
13         t = ListNode(0)
14         while head:
15             head.next = t.next
16             t.next = head
17             head = nextnode
18             if nextnode != None:
19                 nextnode = nextnode.next
20         return t.next
21         # write code here