class Solution:
# 返回ListNode
def ReverseList(self, pHead):
if pHead == None or pHead.next == None: # 链长为0和1的情况
return pHead
# 开始遍历链表,依次的反转
pre = None
cur = pHead
while cur != None:
tmp = cur.next
cur.next = pre # 反置
pre = cur # 反置下一个
cur = tmp
return pre