erhmagerhd

    // does the set contain the point p?
    public boolean contains(Point2D p) {
        return containsAt(root, p, true);
    }

    private boolean containsAt(Node node, Point2D p, boolean isX) {
        if (node == null)
            return false;

        double dist;

        if (isX)
            dist = node.p.x() - p.x();
        else
            dist = node.p.y() - p.y();

        if (node.p.equals(p))
            return true;
        else if (dist > 0)
            return containsAt(node.lb, p, !isX);
        else
            return containsAt(node.rt, p, !isX);
    }