public Point2D nearest(Point2D p) { // a nearest neighbor in the set to p; null if set is empty
Stack<Point2D> stack = new Stack<Point2D>();
nearestNode(root, p, stack, 2.0);
return stack.pop();
}
private void nearestNode(Node2d node, Point2D queryP, Stack<Point2D> stack, double distance) {
if (node == null) return;
if (distance < node.rect.distanceSquaredTo(queryP)) return;
if (queryP.distanceSquaredTo(node.p) < distance) {
stack.push(node.p);
distance = queryP.distanceSquaredTo(node.p);
}
if (node.depth % 2 == 0) {
if (queryP.x() < node.p.x()) {
distance = queryP.distanceSquaredTo(stack.peek());
nearestNode(node.left, queryP, stack, distance);
distance = queryP.distanceSquaredTo(stack.peek());
nearestNode(node.right, queryP, stack, distance);
} else {
distance = queryP.distanceSquaredTo(stack.peek());
nearestNode(node.right, queryP, stack, distance);
distance = queryP.distanceSquaredTo(stack.peek());
nearestNode(node.left, queryP, stack, distance);
}
} else {
if (queryP.y() < node.p.y()) {
distance = queryP.distanceSquaredTo(stack.peek());
nearestNode(node.left, queryP, stack, distance);
distance = queryP.distanceSquaredTo(stack.peek());
nearestNode(node.right, queryP, stack, distance);
} else {
distance = queryP.distanceSquaredTo(stack.peek());
nearestNode(node.right, queryP, stack, distance);
distance = queryP.distanceSquaredTo(stack.peek());
nearestNode(node.left, queryP, stack, distance);
}
}
}
