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<?php |
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namespace drupol\phpermutations; |
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use drupol\phpermutations\Iterators\Combinations; |
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/** |
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* Class Permutations. |
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* |
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* @package drupol\phpermutations |
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*/ |
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class Permutations extends Combinatorics { |
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/** |
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* Count the number of permutations. |
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* |
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* @return int |
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* The number of element. |
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*/ |
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public function count() { |
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return $this->fact(count($this->getDataset())) / $this->fact(count($this->getDataset()) - $this->getLength()); |
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} |
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/** |
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* Return the permutations. |
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* |
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* @return array |
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* The permutations result set. |
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*/ |
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public function generator() { |
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$combinations = new Combinations($this->getDataset(), $this->getLength()); |
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$result = array(); |
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foreach ($combinations->toArray() as $subset) { |
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$set = $subset; |
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$perms = array(); |
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$size = count($subset) - 1; |
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$perm = range(0, $size); |
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$j = 0; |
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do { |
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foreach ($perm as $i) { |
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$perms[$j][] = $set[$i]; |
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} |
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} while ($perm = $this->permute($perm, $size) and ++$j); |
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$result = array_merge($result, $perms); |
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} |
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return $result; |
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} |
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/** |
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* Internal method to compute the permutations. |
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* |
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* @param array $items |
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* The items. |
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* @param int $length |
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* The length. |
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* |
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* @return bool|array |
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* The permutations. |
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*/ |
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protected function permute(array $items, $length) { |
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// Slide down the array looking for where we're smaller than the next guy. |
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for ($i = $length - 1; $i >= 0 && $items[$i] >= $items[$i + 1]; --$i) { |
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} |
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// If this doesn't occur, we've finished our permutations |
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// the array is reversed: (1, 2, 3, 4) => (4, 3, 2, 1) |
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if ($i == -1) { |
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return FALSE; |
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} |
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// Slide down the array looking for a bigger number |
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// than what we found before. |
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for ($j = $length; $items[$j] <= $items[$i]; --$j) { |
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} |
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// Swap them. |
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$this->swap($items[$i], $items[$j]); |
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// Now reverse the elements in between by swapping the ends. |
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for (++$i, $j = $length; $i < $j; ++$i, --$j) { |
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$this->swap($items[$i], $items[$j]); |
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} |
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return $items; |
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} |
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/** |
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* Swap two variables. |
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* |
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* @param mixed $x |
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* The first variable. |
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* @param mixed $y |
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* The second variable. |
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*/ |
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protected function swap(&$x, &$y) { |
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$x ^= $y ^= $x ^= $y; |
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} |
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/** |
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* Transform the iterator into an array. |
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* |
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* @return array |
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* The permutations result set. |
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*/ |
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public function toArray() { |
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$results = array(); |
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foreach ($this->generator() as $value) { |
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$results[] = $value; |
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} |
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return $results; |
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} |
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} |
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drupol /
phpermutations
Loading history...
This check looks for the generic type
arrayas a return type and suggests a more specific type. This type is inferred from the actual code.