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<?php |
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namespace Hexogen\KDTree; |
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use Hexogen\KDTree\Interfaces\ItemInterface; |
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use Hexogen\KDTree\Interfaces\ItemListInterface; |
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use Hexogen\KDTree\Interfaces\KDTreeInterface; |
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use Hexogen\KDTree\Interfaces\NodeInterface; |
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class KDTree implements KDTreeInterface |
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{ |
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/** |
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* @var NodeInterface |
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*/ |
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private $root; |
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/** |
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* @var ItemInterface[]|null array of items or null after tree has been built |
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*/ |
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private $items; |
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/** |
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* @var array |
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*/ |
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private $maxBoundary; |
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/** |
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* @var array |
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*/ |
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private $minBoundary; |
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/** |
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* @var int number of items in the tree |
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*/ |
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private $length; |
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/** |
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* @var int |
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*/ |
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private $dimensions; |
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/** |
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* KDTree constructor. |
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* @param ItemListInterface $itemList |
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*/ |
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public function __construct(ItemListInterface $itemList) |
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{ |
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$this->dimensions = $itemList->getDimensionCount(); |
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$this->items = $itemList->getItems(); |
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$this->length = count($this->items); |
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$this->setBoundaries($this->items); |
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$this->buildTree(); |
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unset($this->items); |
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} |
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/** |
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* Get number of items in the tree |
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* @return int |
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*/ |
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public function getItemCount(): int |
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{ |
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return $this->length; |
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} |
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/** |
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* Get root node |
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* @return NodeInterface|null return node or null if there is no nodes in the tree |
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*/ |
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public function getRoot(): ?NodeInterface |
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{ |
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return $this->root; |
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} |
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/** |
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* Get lower boundary coordinate |
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* @return array |
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*/ |
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public function getMinBoundary(): array |
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{ |
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return $this->minBoundary; |
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} |
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/** |
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* Get upper boundary coordinate |
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* @return array |
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*/ |
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public function getMaxBoundary(): array |
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{ |
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return $this->maxBoundary; |
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} |
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/** |
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* Get number of dimensions in the tree |
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* @return int |
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*/ |
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public function getDimensionCount(): int |
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{ |
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return $this->dimensions; |
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} |
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/** |
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* @param int $lo |
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* @param int $hi |
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* @param int $d |
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* @return Node |
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*/ |
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private function buildSubTree(int $lo, int $hi, int $d): Node |
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{ |
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$mid = (int)(($hi - $lo) / 2) + $lo; |
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$item = $this->select($mid, $lo, $hi, $d); |
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$node = new Node($item); |
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$d++; |
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$d = $d % $this->dimensions; |
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if ($mid > $lo) { |
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$node->setLeft($this->buildSubTree($lo, $mid - 1, $d)); |
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} |
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if ($mid < $hi) { |
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$node->setRight($this->buildSubTree($mid + 1, $hi, $d)); |
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} |
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return $node; |
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} |
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private function exch(int $i, int $j) |
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{ |
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$tmp = $this->items[$i]; |
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$this->items[$i] = $this->items[$j]; |
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$this->items[$j] = $tmp; |
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} |
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/** |
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* @param int $k |
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* @param int $lo |
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* @param int $hi |
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* @param int $d |
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* @return ItemInterface |
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*/ |
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private function select(int $k, int $lo, int $hi, int $d) |
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{ |
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while ($hi > $lo) { |
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$j = $this->partition($lo, $hi, $d); |
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if ($j > $k) { |
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$hi = $j - 1; |
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} elseif ($j < $k) { |
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$lo = $j + 1; |
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} else { |
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return $this->items[$k]; |
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} |
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} |
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return $this->items[$k]; |
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} |
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/** |
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* @param int $lo |
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* @param int $hi |
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* @param int $d |
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* @return int |
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*/ |
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private function partition(int $lo, int $hi, int $d) |
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{ |
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$i = $lo; |
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$j = $hi + 1; |
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$v = $this->items[$lo]; |
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$val = $v->getNthDimension($d); |
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do { |
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while ($this->items[++$i]->getNthDimension($d) < $val && $i != $hi) { |
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} |
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while ($this->items[--$j]->getNthDimension($d) > $val) { |
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} |
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if ($i < $j) { |
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$this->exch($i, $j); |
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} |
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} while ($i < $j); |
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$this->exch($lo, $j); |
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return $j; |
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} |
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/** |
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* Set boundaries for given item list |
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* @param ItemInterface[] $items |
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*/ |
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private function setBoundaries(array $items) |
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{ |
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$this->maxBoundary = []; |
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$this->minBoundary = []; |
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for ($i = 0; $i < $this->dimensions; $i++) { |
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$this->maxBoundary[$i] = -INF; |
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$this->minBoundary[$i] = INF; |
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} |
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foreach ($items as $item) { |
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for ($i = 0; $i < $this->dimensions; $i++) { |
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$this->maxBoundary[$i] = max($this->maxBoundary[$i], $item->getNthDimension($i)); |
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$this->minBoundary[$i] = min($this->minBoundary[$i], $item->getNthDimension($i)); |
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} |
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} |
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} |
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/** |
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* Build kd tree |
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*/ |
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private function buildTree() |
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{ |
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if ($this->length > 0) { |
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$hi = $this->length - 1; |
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$mid = (int)($hi / 2); |
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$item = $this->select($mid, 0, $hi, 0); |
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$this->root = new Node($item); |
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$nextDimension = 1 % $this->dimensions; |
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if ($mid > 0) { |
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$this->root->setLeft($this->buildSubTree(0, $mid - 1, $nextDimension)); |
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} |
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if ($mid < $hi) { |
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$this->root->setRight($this->buildSubTree($mid + 1, $hi, $nextDimension)); |
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} |
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} |
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} |
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} |
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hexogen /
kdtree
