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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 DepthFirstPath |
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* @package TemplesOfCode\NodesAndEdges\DFS |
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*/ |
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class DepthFirstPath |
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{ |
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/** |
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* @var Graph |
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*/ |
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private $graph; |
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/** |
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* @var bool[] |
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*/ |
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private $marked; |
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/** |
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* @var int[] |
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*/ |
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private $edgeTo; |
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/** |
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* @var int |
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*/ |
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private $sourceVertex; |
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/** |
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* DepthFirstPath constructor. |
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* @param Graph $graph |
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* @param int $sourceVertex |
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*/ |
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public function __construct(Graph $graph, int $sourceVertex) |
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{ |
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// validate this vertex in the context of the given graph |
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Graph::validateVertex($sourceVertex, $graph->getVertices()); |
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// init |
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$this->marked = array_fill(0, $graph->getVertices(), false); |
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// set |
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$this->graph = $graph; |
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// set |
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$this->sourceVertex = $sourceVertex; |
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// execute DFS logic |
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$this->dfs($sourceVertex); |
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} |
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/** |
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* Depth first search from $vertex |
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* |
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* @param int $vertex |
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*/ |
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private function dfs(int $vertex) |
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{ |
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// set this vertex as marked |
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$this->marked[$vertex] = true; |
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// iterate over the the vertices incident to $vertex |
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foreach ($this->graph->adjacent($vertex) as $w) { |
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// if we have not visited this vertex yet.. |
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if (!$this->marked[$w]) { |
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// set |
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$this->edgeTo[$w] = $vertex; |
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// lets visit |
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$this->dfs($w); |
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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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* @return bool |
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*/ |
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public function hasPathTo(int $vertex) |
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{ |
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// validate this vertex in the context of the given graph |
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Graph::validateVertex($vertex, $this->graph->getVertices()); |
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// return |
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return $this->marked[$vertex]; |
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} |
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/** |
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* @param int $vertex |
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* @return array |
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*/ |
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public function pathTo(int $vertex) |
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{ |
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// validate this vertex in the context of the given graph |
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Graph::validateVertex($vertex, $this->graph->getVertices()); |
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// check if there is a path |
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if (!$this->hasPathTo($vertex)) { |
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// empty case |
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return null; |
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} |
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// init |
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$path = []; |
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// pop into the stack |
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for ($x = $vertex; $x != $this->sourceVertex; $x = $this->edgeTo[$x]) { |
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// pop into stack |
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array_unshift($path, $x); |
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} |
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// pop the source into the stack |
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array_unshift($path, $this->sourceVertex); |
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// return the stack |
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return $path; |
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} |
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} |
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templesofcode /
nodes-and-edges
