LinkedList Palindrome

# 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 head is None:
            return True
        
        length = 0
        node = head
        
        while node:
            node = node.next
            length += 1
        
        _, res = self.recIsPal(head, 0, length-1)
        return res
        
        
    def recIsPal(self, node, c1, c2):
        """
        :type node: ListNode leftNode
        :type c1: leftNode index
        :type c2: rightNode index
        :rtype: (rightNode, bool)
        """
        # when list lenght is odd
        if c2 == c1:
            return node.next, True
        
        # when list length is even
        if c2 == c1 + 1:
            return node.next.next, node.val == node.next.val
        
        nodeLast, isPal = self.recIsPal(node.next, c1+1, c2-1)
        
        return nodeLast.next, node.val == nodeLast.val and isPal