Tag: stack

let isPalindrome = function(head) {

    let slow = head, fast = head, val = [slow.val];

    while (fast.next) {
        if (fast.next.next) {
            fast = fast.next.next;
            slow = slow.next;
            val.push(slow.val);
        }
        else {
            fast = fast.next;
            slow = slow.next;
        }
    }

    while (slow) {
        if (slow.val !== val.pop()) {
            return false;
        }
        slow = slow.next;
    }

    return val.length === 0;
};