牛客网hoot200(二)

    public boolean isPail (ListNode head) {
        // write code here
          if (head.next == null){
            return true;
        }
        if (head.next.next == null){
            return false;
        }

        ListNode slow = head;
        ListNode fast = head;
        while (fast != null && fast.next != null){
            slow = slow.next;
            fast = fast.next.next;
        }
        ListNode reserveList = reserve(slow);
        ListNode pre = reserveList;
        ListNode cur = head;

        
        while (pre.next != null && cur.next !=null){
            if (pre.val != cur.val){
                ret