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<?php declare(strict_types=1);
namespace Stratadox\PuzzleSolver\SearchStrategy;
use Stratadox\PuzzleSolver\Puzzle;
use const INF;
/**
* Worse-Than-Best Solution Skipper
*
* The Worse-Than-Best Solution Skipper keeps track of the lowest cost of the
* solutions that have been found during the search. Each time a node is
* encountered of which the path cost is more than the cost of the cheapest
* solution that has already been found, the node is skipped.
* @author Stratadox
*/
final class WorseThanBestSolutionSkipper implements SearchStrategy
{
/** @var float */
private $lowestSolutionCost = INF;
/** @var SearchStrategy */
private $search;
private function __construct(SearchStrategy $search)
$this->search = $search;
}
public static function forThe(SearchStrategy $search): self
return new self($search);
public function isOngoing(): bool
return $this->search->isOngoing();
public function consider(Puzzle $puzzle): bool
if ($puzzle->movesSoFar()->cost() > $this->lowestSolutionCost) {
return false;
return $this->search->consider($puzzle);
public function nextCandidate(): Puzzle
$puzzle = $this->search->nextCandidate();
if (
$puzzle->isSolved() &&
($cost = $puzzle->movesSoFar()->cost()) < $this->lowestSolutionCost
) {
$this->lowestSolutionCost = $cost;
return $puzzle;
Stratadox /
PuzzleSolver
