# Definition for singly-linked list.

# class ListNode:

# def __init__(self, x):

# self.val = x

# self.next = None

class Solution:

def isPalindrome(self, head):

"""

:type head: ListNode

:rtype: bool

"""

rev = None

slow = fast = head

while fast and fast.next:

fast = fast.next.next

rev, rev.next, slow = slow, rev, slow.next

if fast:

slow = slow.next

while slow and slow.val == rev.val:

slow = slow.next

rev = rev.next

return not rev

class Solution:

def isPalindrome(self, head):

"""

:type head: ListNode

:rtype: bool

"""

rev = nxt = None

slow = fast = head

while fast and fast.next:

fast = fast.next.next

nxt = slow.next

slow.next = rev

rev = slow

slow = nxt

if fast:

slow = slow.next

while slow and slow.val == rev.val:

slow = slow.next

rev = rev.next

return not rev