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<?php |
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namespace TemplesOfCode\NodesAndEdges\DFS; |
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use TemplesOfCode\NodesAndEdges\Graph; |
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/** |
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* Class DepthFirstOrder |
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* @package TemplesOfCode\NodesAndEdges |
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*/ |
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class DepthFirstOrder |
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{ |
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/** |
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* @var bool[] |
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*/ |
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protected $marked; |
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/** |
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* @var Graph |
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*/ |
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protected $graph; |
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/** |
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* @var array |
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*/ |
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private $pre; |
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/** |
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* @var array |
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*/ |
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private $post; |
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/** |
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* @var array |
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*/ |
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private $reversePost; |
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/** |
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* DepthFirstOrder constructor. |
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* |
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* @param Graph $graph |
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*/ |
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public function __construct(Graph $graph) |
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{ |
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// init |
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$this->pre = []; |
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// init |
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$this->post = []; |
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// init |
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$this->reversePost = []; |
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// set |
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$this->graph = $graph; |
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// set |
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$vertices = $graph->getVertices(); |
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// set |
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$this->marked = array_fill(0, $vertices, false); |
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// iterate over the vertices |
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for ($vertex = 0; $vertex < $vertices; $vertex++) { |
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// check for visit |
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if (!$this->marked[$vertex]) { |
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// execute DFS logic |
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$this->dfs($vertex); |
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} |
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} |
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} |
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/** |
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* @param int $vertex |
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*/ |
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protected function dfs(int $vertex) |
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{ |
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// enqueue $vertex - add to end |
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array_push($this->pre, $vertex); |
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// mark the visit |
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$this->marked[$vertex] = true; |
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// get neighbors |
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$neighbors = $this->graph->adjacent($vertex); |
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// iterate over the set |
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foreach ($neighbors as $w) { |
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// check for previous visit |
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if (!$this->marked[$w]) { |
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// has not been visited yet |
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$this->dfs($w); |
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} |
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} |
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// enqueue $vertex - add to end |
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array_push($this->post, $vertex); |
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// push to the reverse post stack - add to beginning |
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array_unshift($this->reversePost, $vertex); |
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} |
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/** |
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* @return array |
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*/ |
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public function preorder() |
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{ |
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return $this->pre; |
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} |
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/** |
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* @return array |
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*/ |
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public function postorder() |
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{ |
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return $this->post; |
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} |
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/** |
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* @return array |
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*/ |
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public function reversePostorder() |
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{ |
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return $this->reversePost; |
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} |
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} |
templesofcode /
nodes-and-edges
