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<?php |
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declare(strict_types=1); |
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namespace App\Component\Math\Graph\Path; |
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/** |
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* Find least number of hops between nodes collection. |
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* Graph should be considered as oriented. |
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* @author Pierre Fromager <[email protected]> |
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*/ |
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class Min |
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{ |
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/** |
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* graph |
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* |
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* @var array |
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*/ |
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protected $graph; |
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/** |
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* visited |
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* |
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* @var array |
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*/ |
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protected $visited = []; |
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/** |
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* instanciate |
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* |
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* @param array $graph |
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*/ |
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public function __construct(array $graph) |
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{ |
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$this->graph = $graph; |
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} |
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/** |
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* return path search as array |
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* |
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* @param string $origin |
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* @param string $destination |
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* @return array |
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*/ |
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public function path(string $origin, string $destination): array |
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{ |
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// check exists origin destination |
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if (!isset($this->graph[$origin]) || !isset($this->graph[$destination])) { |
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return []; |
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} |
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// mark all nodes as unvisited |
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foreach ($this->graph as $vertex => $adj) { |
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$this->visited[$vertex] = false; |
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} |
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// create an empty queue |
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$q = new \SplQueue(); |
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// enqueue the origin vertex and mark as visited |
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$q->enqueue($origin); |
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$this->visited[$origin] = true; |
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// this is used to track the path back from each node |
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$path = []; |
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$path[$origin] = new \SplDoublyLinkedList(); |
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$path[$origin]->setIteratorMode( |
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\SplDoublyLinkedList::IT_MODE_FIFO | \SplDoublyLinkedList::IT_MODE_KEEP |
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); |
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$path[$origin]->push($origin); |
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// while queue is not empty and destination not found |
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while (!$q->isEmpty() && $q->bottom() != $destination) { |
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$t = $q->dequeue(); |
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if (!empty($this->graph[$t])) { |
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// for each adjacent neighbor |
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foreach ($this->graph[$t] as $vertex) { |
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if (!$this->visited[$vertex]) { |
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// if not yet visited, enqueue vertex and mark |
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// as visited |
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$q->enqueue($vertex); |
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$this->visited[$vertex] = true; |
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// add vertex to current path |
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$path[$vertex] = clone $path[$t]; |
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$path[$vertex]->push($vertex); |
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} |
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} |
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} |
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} |
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return (isset($path[$destination])) ? iterator_to_array($path[$destination]) : []; |
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} |
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} |
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pierre-fromager /
nymfonya
