Given the head of a singly linked list return true if it is a palindrome or false otherwise..
Example 1:
Input: head = [1,2,2,1] Output:true
Example 2:
Input: head = [1,2] Output: false
Constraints:
- The number of nodes in the list is the range
[0, 5000]. 0 <= Node.val <= 9
Follow up:Could you do it in O(n) time and O(1) space?