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<?php |
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declare(strict_types=1); |
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namespace loophp\collection\Operation; |
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use Closure; |
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use Generator; |
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use loophp\collection\Contract\Operation; |
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use loophp\collection\Transformation\All; |
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use loophp\collection\Transformation\Count; |
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use function array_slice; |
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use function count; |
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/** |
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* Class Combinate. |
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*/ |
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final class Combinate implements Operation |
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{ |
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/** |
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* @var int|null |
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*/ |
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private $length; |
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/** |
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* Permutations constructor. |
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* |
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* @param int $length |
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*/ |
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public function __construct(?int $length = null) |
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{ |
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$this->length = $length; |
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} |
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/** |
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* @param array<mixed> $dataset |
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* @param int $length |
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* |
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* @return Generator<array<mixed>> |
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*/ |
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public function getCombinations(array $dataset, int $length): Generator |
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{ |
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$originalLength = count($dataset); |
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$remainingLength = $originalLength - $length + 1; |
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for ($i = 0; $i < $remainingLength; ++$i) { |
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$current = $dataset[$i]; |
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if (1 === $length) { |
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yield [$current]; |
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} else { |
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$remaining = array_slice($dataset, $i + 1); |
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foreach ($this->getCombinations($remaining, $length - 1) as $permutation) { |
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array_unshift($permutation, $current); |
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yield $permutation; |
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} |
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} |
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} |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function on(iterable $collection): Closure |
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{ |
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$length = $this->length; |
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$getPermutation = function (array $dataset, int $length): Generator { |
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return $this->getCombinations($dataset, $length); |
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}; |
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return static function () use ($length, $collection, $getPermutation): Generator { |
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$dataset = (new All())->on($collection); |
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if (0 < $length) { |
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return yield from $getPermutation($dataset, $length); |
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} |
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$collectionSize = count($dataset); |
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if (0 === $length) { |
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return yield from $getPermutation($dataset, $collectionSize); |
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} |
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for ($i = 1; $i <= $collectionSize; ++$i) { |
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yield from $getPermutation($dataset, $i); |
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} |
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}; |
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} |
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} |
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loophp /
collection
