public boolean remove(int index) {
        if(index<1 || index>size())
            return false;

        Node current = head; // 这里从head之后开始rm
        for(int i=1; i<index; i++) {
            if(current.next == null)
                return false;

            current = current.next;
        }
        current.next = current.next.next;
        size--;
        return true;
    }