链表_leetcode234

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
 def isPalindrome(self, head):
 """
 :type head: ListNode
 :rtype: bool
 """

 if not head :
 return True

 if not head.next :
 return True

 else :
 slow = fast = head

 while fast.next and fast.next.next:
 slow = slow.next
 fast = fast.next.next


 head2 = slow.next

 dummyHead = ListNode(0)
 dummyHead.next = head2

 p = head2.next
 head2.next = None

 while p:
 nextP = p.next
 p.next = dummyHead.next
 dummyHead.next = p
 p = nextP


 p1 =head

 head2 = dummyHead.next

 p2 = head2



 while p2:
 if p1.val == p2.val:
 p1 = p1.next
 p2 = p2.next
 else:
 return False

 return True