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<?php declare(strict_types=1); |
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namespace Stratadox\PuzzleSolver\SearchStrategy; |
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use Stratadox\PuzzleSolver\Move; |
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use Stratadox\PuzzleSolver\Puzzle; |
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/** |
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* Duplicate Node Skipper |
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* |
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* Duplicate Node Skipper prevents paths from getting into loops. |
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* Before considering a new candidate, all previous puzzle states are compared |
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* with the new state. If the new puzzle state was already reached on this very |
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* path, the candidate is considered a loop and gets rejected. |
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* |
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* Decorator for other search strategies. |
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* |
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* @author Stratadox |
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*/ |
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final class DuplicateNodeSkipper implements SearchStrategy |
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{ |
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/** @var SearchStrategy */ |
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private $search; |
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/** @var Puzzle */ |
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private $puzzle; |
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public function __construct(SearchStrategy $search, Puzzle $puzzle) |
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{ |
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$this->search = $search; |
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$this->puzzle = $puzzle; |
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} |
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public static function forThe(Puzzle $puzzle, SearchStrategy $search): SearchStrategy |
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{ |
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return new self($search, $puzzle); |
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} |
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public function isOngoing(): bool |
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{ |
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return $this->search->isOngoing(); |
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} |
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public function consider(Puzzle $puzzle): bool |
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{ |
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if ($this->shouldSkip($this->puzzle, $puzzle->representation(), ...$puzzle->movesSoFar())) { |
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return false; |
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} |
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return $this->search->consider($puzzle); |
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} |
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public function nextCandidate(): Puzzle |
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{ |
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return $this->search->nextCandidate(); |
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} |
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private function shouldSkip( |
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Puzzle $visited, |
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string $current, |
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Move ...$moves |
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): bool { |
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foreach ($moves as $move) { |
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if ($visited->representation() === $current) { |
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return true; |
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} |
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$visited = $visited->afterMaking($move); |
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} |
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return false; |
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} |
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} |
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Stratadox /
PuzzleSolver
