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<?php |
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namespace drupol\phpermutations\Iterators; |
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use drupol\phpermutations\Combinatorics; |
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use drupol\phpermutations\IteratorInterface; |
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/** |
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* Class FiniteGroup. |
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* |
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* The finite group is an abelian finite cyclic group. |
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*/ |
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class FiniteGroup extends Combinatorics implements IteratorInterface |
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{ |
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/** |
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* The group size. |
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* |
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* @var int |
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*/ |
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protected $size; |
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/** |
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* The group. |
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* |
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* @var int[] |
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*/ |
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protected $group; |
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/** |
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* The key. |
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* |
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* @var int |
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*/ |
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protected $key; |
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/** |
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* Combinatorics constructor. |
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*/ |
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public function __construct() |
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{ |
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parent::__construct([], null); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function current() |
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{ |
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return current($this->group); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function next() |
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{ |
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++$this->key; |
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next($this->group); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function valid() |
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{ |
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return isset($this->group[$this->key()]); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function rewind() |
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{ |
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$this->key = 0; |
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} |
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/** |
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* Count elements of an object. |
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* |
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* @return int |
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* The number of element |
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*/ |
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public function count() |
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{ |
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return count($this->group); |
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} |
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/** |
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* Set the group size. |
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* |
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* @param int $size |
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* The size |
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*/ |
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public function setSize($size) |
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{ |
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$this->size = $size; |
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$this->computeGroup(); |
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} |
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/** |
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* Get the group size. |
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* |
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* @return int |
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* The size |
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*/ |
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public function getSize() |
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{ |
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return (int) $this->size; |
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} |
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/** |
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* Get the order. |
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* |
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* @param int $generator |
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* The generator |
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* |
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* @return int |
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* The order |
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*/ |
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public function order($generator) |
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{ |
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$result = []; |
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foreach (range(1, $this->getSize() - 1) as $number) { |
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$value = ($generator ** $number) % $this->getSize(); |
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$result[$value] = $value; |
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} |
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return count($result); |
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} |
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/** |
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* Clean out the group from unwanted values. |
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*/ |
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private function computeGroup() |
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{ |
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$this->group = []; |
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foreach (range(1, $this->getSize() - 1) as $number) { |
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if (1 === $this->gcd($number, $this->getSize() - 1)) { |
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$this->group[] = $number; |
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} |
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} |
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} |
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/** |
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* Get the greater common divisor between two numbers. |
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* |
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* @param int $a |
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* The first number |
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* @param int $b |
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* The second number |
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* |
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* @return int |
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* The greater common divisor between $a and $b |
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*/ |
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private function gcd($a, $b) |
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{ |
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return $b ? $this->gcd($b, $a % $b) : $a; |
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} |
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} |
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drupol /
phpermutations
