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<?php declare(strict_types=1);
namespace Stratadox\PuzzleSolver\SearchStrategy;
use Stratadox\PuzzleSolver\Puzzle;
/**
* Visited Node Skipper
*
* The Visited Node Skipper keeps a list of puzzle states that have already been
* encountered during the search to skip candidates when they are about to be
* considered for a second time.
* Decorator for other search strategies.
* @author Stratadox
*/
final class VisitedNodeSkipper implements SearchStrategy
{
/** @var SearchStrategy */
private $search;
/** @var bool[] */
private $visited = [];
public function __construct(SearchStrategy $search)
$this->search = $search;
}
public static function forThe(SearchStrategy $search): SearchStrategy
return new self($search);
public function isOngoing(): bool
return $this->search->isOngoing();
public function consider(Puzzle $puzzle): bool
if (isset($this->visited[$puzzle->representation()])) {
return false;
return $this->search->consider($puzzle);
public function nextCandidate(): Puzzle
$state = $this->search->nextCandidate();
if (!$state->isSolved()) {
$this->visited[$state->representation()] = true;
return $state;
Stratadox /
PuzzleSolver
