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<?php |
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namespace TemplesOfCode\NodesAndEdges; |
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use InvalidArgumentException; |
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/** |
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* Class Digraph |
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* @package TemplesOfCode\NodesAndEdges |
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*/ |
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class Digraph extends Graph |
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{ |
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/** |
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* @var array |
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*/ |
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protected $inDegree; |
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/** |
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* Digraph constructor. |
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* |
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* @param int $vertices |
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* @param array|null $adjacencyList |
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*/ |
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public function __construct(int $vertices, array $adjacencyList = null) |
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{ |
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// delegate to parent tasks |
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parent::__construct($vertices, $adjacencyList); |
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// init |
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$this->inDegree = array_fill(0, $vertices, 0); |
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} |
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/** |
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* @param int $v |
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* @param int $w |
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*/ |
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public function addEdge(int $v, int $w) |
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{ |
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// validate the vertex |
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Graph::validateVertex($v, $this->vertices); |
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// validate the vertex |
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Graph::validateVertex($w, $this->vertices); |
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// link the edge to v |
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$this->adjacencyList[$v][] = $w; |
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// increment the in-degree |
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$this->inDegree[$w]++; |
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// increment the tracker |
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$this->edges++; |
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} |
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/** |
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* Returns the number of directed edges incident from vertex v |
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* This is known as the out-degree of vertex v |
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* |
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* @param int $v the vertex |
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* @return int the out-degree of vertex v |
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* @throws InvalidArgumentException unless 0 <= v < V |
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*/ |
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public function outDegree(int $v) |
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{ |
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// validate |
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Graph::validateVertex($v, $this->getVertices()); |
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// return the count |
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return count($this->adjacencyList[$v]); |
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} |
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/** |
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* Returns the number of directed edges incident to vertex v |
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* This is known as the in-degree of vertex v |
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* |
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* @param int $v the vertex |
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* @return int the in-degree of vertex v |
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* @throws InvalidArgumentException unless 0 <= v < V |
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*/ |
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public function inDegree(int $v) |
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{ |
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// validate it |
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Graph::validateVertex($v, $this->getVertices()); |
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// return the count |
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return $this->inDegree[$v]; |
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} |
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/** |
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* Returns the reverse of the digraph. |
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* |
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* @return Graph the reverse of the digraph |
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*/ |
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public function reverse() |
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{ |
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// get set |
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$vertices = $this->getVertices(); |
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// init |
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$reverse = new Digraph($vertices); |
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// iterate over the vertices |
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for ($vertex = 0; $vertex < $vertices; $vertex++) { |
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// get the neighbors |
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$neighbors = $this->adjacent($vertex); |
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// iterate over the neighbors |
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foreach ($neighbors as $w) { |
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// add the reverse |
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$reverse->addEdge($w, $vertex); |
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} |
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} |
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// return the new digraph |
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return $reverse; |
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} |
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/** |
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* Initializes an edge-weighted graph from an input stream. |
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* The format is the number of $vertices, |
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* followed by the number of $edges , |
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* followed by $edges pairs of vertices and edge weights, |
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* with each entry separated by whitespace. |
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* |
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* @param resource $handle the input stream |
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* @return Digraph |
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*/ |
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public static function fromStream($handle) |
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{ |
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// sanity check |
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if (!is_resource($handle) || $handle === null) { |
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// bad state |
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throw new InvalidArgumentException( |
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'argument is null' |
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); |
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} |
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// parse V and E |
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list( |
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$vertices, |
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$edges |
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) = self::parseGraphVEFromResource($handle); |
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// instantiate a new graph |
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$graph = new Digraph($vertices); |
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// read in the edges |
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for ($i = 0; $i < $edges; $i++) { |
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// fet from source |
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$raw = fgets($handle); |
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// parse data |
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list ( |
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$v, |
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$w |
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) = self::parseEdge($raw, $vertices); |
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// add it to the graph |
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$graph->addEdge($v, $w); |
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} |
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// rewind the stream |
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rewind($handle); |
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// return the built graph |
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return $graph; |
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} |
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/** |
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* Initializes a new digraph that is a deep copy of $g |
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* |
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* @param Digraph $g |
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* @return Digraph |
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*/ |
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public static function fromGraph(Digraph $g) |
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{ |
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// make sure there is a references |
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if (is_null($g)) { |
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// bad state |
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throw new InvalidArgumentException('argument is null'); |
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} |
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// get the number of vertices |
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$vertices = $g->getVertices(); |
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// init |
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$adjacencyList = []; |
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// iterate over the vertices |
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for ($vertex = 0; $vertex < $vertices; $vertex++) { |
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// get the adjacent vertices |
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$adjacencyList[$vertex] = $g->adjacent($vertex); |
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} |
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// return the new graph |
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return new Digraph($vertices, $adjacencyList); |
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} |
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/** |
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* |
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* @param string $file |
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* @return Digraph |
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*/ |
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public static function fromFile(string $file) |
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{ |
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// open the stream for reading |
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if (!$handle = fopen($file, 'r')) { |
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throw new InvalidArgumentException('could not open stream'); |
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} |
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// parse V and E |
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list( |
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$vertices, |
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$edges |
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) = self::parseGraphVEFromResource($handle); |
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// instantiate a new graph |
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$graph = new Digraph($vertices); |
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// read in the edges |
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for ($i = 0; $i < $edges; $i++) { |
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// fet from source |
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$raw = fgets($handle); |
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// parse data |
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list ( |
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$v, |
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$w |
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) = self::parseEdge($raw, $vertices); |
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// add to the graph |
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$graph->addEdge($v, $w); |
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} |
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// close the stream |
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fclose($handle); |
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// return the built graph |
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return $graph; |
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} |
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/** |
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* |
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* @param string $graph |
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* @return Digraph |
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*/ |
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public static function fromString(string $graph) |
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{ |
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// parse the lines |
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$lines = explode("\n", $graph); |
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// parse V and E |
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list ( |
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$vertices, |
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$edges |
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) = self::parseGraphVEFromString($lines[0], $lines[1]); |
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// instantiate a new graph |
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$graph = new Digraph($vertices); |
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// read in the edges |
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for ($i = 0; $i < $edges; $i++) { |
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// fet from source |
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$raw = $lines[$i+2]; |
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// parse data |
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list ( |
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$v, |
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$w |
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) = self::parseEdge($raw, $vertices); |
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// add to the graph |
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$graph->addEdge($v, $w); |
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} |
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// return the built graph |
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return $graph; |
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} |
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} |