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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 function array_slice; |
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use function count; |
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/** |
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* @immutable |
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* |
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* @template TKey |
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* @template T |
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*/ |
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final class Combinate extends AbstractOperation |
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{ |
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public function __invoke(): Closure |
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{ |
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return static function (?int $length = null): Closure { |
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$getCombinations = |
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/** |
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* @param array<int, T> $dataset |
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* |
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* @return Generator<array<int, T>> |
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*/ |
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static function (array $dataset, int $length) use (&$getCombinations): Generator { |
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for ($i = 0; count($dataset) - $length >= $i; ++$i) { |
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if (1 === $length) { |
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yield [$dataset[$i]]; |
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continue; |
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} |
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/** @var array<int, T> $permutation */ |
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foreach ($getCombinations(array_slice($dataset, $i + 1), $length - 1) as $permutation) { |
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array_unshift($permutation, $dataset[$i]); |
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yield $permutation; |
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} |
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} |
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}; |
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return |
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/** |
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* @param iterable<TKey, T> $iterable |
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* |
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* @return Generator<int, array<int, T>> |
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*/ |
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static function (iterable $iterable) use ($length, $getCombinations): Generator { |
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/** @psalm-suppress InvalidOperand */ |
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$dataset = [...$iterable]; |
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if (0 < $length) { |
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return yield from $getCombinations($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 $getCombinations($dataset, $collectionSize); |
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} |
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2 |
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for ($i = 1; $i <= $collectionSize; ++$i) { |
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yield from $getCombinations($dataset, $i); |
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} |
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}; |
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}; |
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} |
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} |
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loophp /
collection
