/**
     * 链表转为list, 采用双指针,操作链表双指针个,由于没有pre指针不好操作,转为list
     *
     * @param head
     * @return
     */
    public boolean isPail(ListNode head) {
        // write code here
        List<Integer> res = new ArrayList<>();
        while (head != null) {
            res.add(head.val);
            head = head.next;
        }
        for (int x = 0, y = res.size() - 1; x < y; x++, y--) {
            if (!res.get(x).equals(res.get(y))) {
                return false;
            }
        }
        return true;
    }