""" 
Definition of ListNode 
 
class ListNode(object): 
 
 def __init__(self, val, next=None): 
  self.val = val 
  self.next = next 
""" 
class Solution: 
 """ 
 @param head: The first node of the linked list. 
 @return: You should return the head of the reversed linked list. 
     Reverse it in-place. 
 """ 
 def reverse(self, head): 
  temp = None 
  while head: 
   cur = head.next 
   head.next = temp 
   temp = head 
   head = cur 
  return temp 
  # write your code here 

""" 
Definition of ListNode 
 
class ListNode(object): 
 
 def __init__(self, val, next=None): 
  self.val = val 
  self.next = next 
""" 
class Solution: 
 """ 
 @param head: The first node of the linked list. 
 @return: You should return the head of the reversed linked list. 
     Reverse it in-place. 
 """ 
 def reverse(self, head): 
  if head is None: 
   return head 
  dummy = ListNode(-1) 
  dummy.next = head 
  pre, cur = head, head.next 
  while cur: 
   temp = cur 
   # 把摘链的地方连起来 
   pre.next = cur.next 
   cur = pre.next 
   temp.next = dummy.next 
   dummy.next = temp 
  return dummy.next 
  # write your code here