public List<T> findClosestNeighbours(double x, double y, double radius, int maxCount) {
NearestNeighborGatherer<T> gatherer = new NearestNeighborGatherer<>(x, y, radius, maxCount);
if (root != null) {
root.findNearestNeighbors(0, gatherer);
}
return gatherer.getResults();
}
@Override
public void findNearestNeighbors(int depth, NearestNeighborGatherer<T> gatherer) {
final int visitedTree;
final boolean xAxis = (depth % 2) == 0;
if (xAxis) {
// split on X-axis
if (gatherer.x < splitValue) {
// left subtree
visitedTree = LEFT;
if (left != null) {
if (left.isLeaf()) {
gatherer.addCandidate((LeafNode<T>) left);
} else {
left.findNearestNeighbors(depth + 1, gatherer);
}
}
} else {
// right subtree
visitedTree = RIGHT;
if (right != null) {
if (right.isLeaf()) {
gatherer.addCandidate((LeafNode<T>) right);
} else {
right.findNearestNeighbors(depth + 1, gatherer);
}
}
}
} else // split on Y-axis
{
if (gatherer.y < splitValue) {
// left subtree
visitedTree = LEFT;
if (left != null) {
if (left.isLeaf()) {
gatherer.addCandidate((LeafNode<T>) left);
} else {
left.findNearestNeighbors(depth + 1, gatherer);
}
}
} else {
// right subtree
visitedTree = RIGHT;
if (right != null) {
if (right.isLeaf()) {
gatherer.addCandidate((LeafNode<T>) right);
} else {
right.findNearestNeighbors(depth + 1, gatherer);
}
}
}
}
if (!gatherer.isFull()) {
// check if the other subtree may contain values that are closer
// than the point farthest out we've found so far
final double distance;
if (xAxis) {
distance = Math.abs(gatherer.x - splitValue);
} else {
distance = Math.abs(gatherer.y - splitValue);
}
final boolean isWithinRadius = distance <= gatherer.radius;
if (right != null && isWithinRadius && visitedTree == LEFT) {
if (right.isLeaf()) {
gatherer.addCandidate((LeafNode<T>) right);
} else {
right.findNearestNeighbors(depth + 1, gatherer);
}
} else if (left != null && isWithinRadius && visitedTree == RIGHT) {
if (left.isLeaf()) {
gatherer.addCandidate((LeafNode<T>) left);
} else {
left.findNearestNeighbors(depth + 1, gatherer);
}
}
}
}
