686. Palindrome Linked List
Given the *head* of a singly linked list, determine whether the list is a palindrome.
The first line of input contains the size of the linked list. The second line contains the elements of the linked list.
Print True if the linked list is a palindrome, and False otherwise.
6 2 3 4 4 3 2
The number of nodes in the list is between 1 and 105, inclusive. Each node's value is an integer between 0 and 9, inclusive.