public void setElement(int r, int c, int v){
        ListIterator<Node> iterator = element.listIterator();
        Node cur = new Node(0, 0, 0);
        while (iterator.hasNext()) {
            cur = iterator.next();
            if ((cur.getRow() >= r) & (cur.getColumn() >= c)){
                if ((cur.getRow() == r) & (cur.getColumn() == c)){
                    iterator.previous();
                    iterator.remove();
                    iterator.add(new Node(r, c, v));
                }
                iterator.previous();
                iterator.add(new Node (r, c, v));
                return;
            }
        }
        iterator.add(new Node (r, c, v));
    }

    public int getElement(int r, int c){
        ListIterator<Node> iterator = element.listIterator();
        Node cur = new Node(0, 0, 0);
        while (iterator.hasNext()) {
            cur = iterator.next();
            if ((cur.getRow() == r) & (cur.getColumn() == c)){
                return cur.getValue();
            }
            if ((cur.getRow() >= r) & (cur.getColumn() > c)) return 0;
        }
        return 0;
    }