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<?php |
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/** |
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* Box packing (3D bin packing, knapsack problem). |
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* |
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* @author Doug Wright |
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*/ |
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namespace DVDoug\BoxPacker; |
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/** |
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* List of items to be packed, ordered by volume. |
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* |
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* @author Doug Wright |
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*/ |
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class ItemList extends \SplMaxHeap |
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{ |
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/** |
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* Compare elements in order to place them correctly in the heap while sifting up. |
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* |
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* @see \SplMaxHeap::compare() |
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* |
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* @param mixed $itemA |
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* @param mixed $itemB |
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* |
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* @return int |
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*/ |
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public function compare($itemA, $itemB) |
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{ |
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if ($itemA->getVolume() > $itemB->getVolume()) { |
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return 1; |
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} elseif ($itemA->getVolume() < $itemB->getVolume()) { |
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return -1; |
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} elseif ($itemA->getWeight() !== $itemB->getWeight()) { |
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return $itemA->getWeight() - $itemB->getWeight(); |
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} elseif ($itemA->getDescription() < $itemB->getDescription()) { |
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return 1; |
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} else { |
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return -1; |
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} |
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} |
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/** |
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* Do a bulk create. |
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* |
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* @param Item[] $items |
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* @return ItemList |
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*/ |
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public static function fromArray(array $items) |
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{ |
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$list = new static(); |
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foreach ($items as $item) { |
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$list->insert($item); |
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} |
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return $list; |
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} |
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/** |
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* Get copy of this list as a standard PHP array. |
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* |
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* @return Item[] |
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*/ |
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public function asArray() |
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{ |
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$return = []; |
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foreach (clone $this as $item) { |
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$return[] = $item; |
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} |
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return $return; |
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} |
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/** |
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* @internal |
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* |
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* @param int $n |
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* @return ItemList |
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*/ |
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public function topN($n) |
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{ |
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$workingList = clone $this; |
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$topNList = new self(); |
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$i = 0; |
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while(!$workingList->isEmpty() && $i < $n) { |
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$topNList->insert($workingList->extract()); |
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$i++; |
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} |
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return $topNList; |
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} |
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/** |
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* Remove item from list. |
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* |
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* @param Item $item |
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*/ |
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public function remove(Item $item) |
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{ |
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$workingSet = []; |
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while (!$this->isEmpty()) { |
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$workingSet[] = $this->extract(); |
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} |
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$removed = false; // there can be multiple identical items, ensure that only 1 is removed |
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foreach ($workingSet as $workingSetItem) { |
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if (!$removed && $workingSetItem === $item) { |
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$removed = true; |
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} else { |
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$this->insert($workingSetItem); |
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} |
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} |
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} |
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} |
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dvdoug /
BoxPacker
