private void insertNoEmpty(KdNode tree, Point2D p, boolean vertical) {
if (p.equals(tree.p)) return;
double keyintree = vertical ? tree.p.y() : tree.p.x();
double keytocmp = vertical ? p.y() : p.x();
if (keytocmp < keyintree) {
if (tree.l == null) {
size++;
tree.l = new KdNode(p);
} else insertNoEmpty(tree.l, p, !vertical);
} else {
if (tree.r == null) {
size++;
tree.r = new KdNode(p);
} else insertNoEmpty(tree.r, p, !vertical);
}
}
