123 lines
3.4 KiB
PHP
123 lines
3.4 KiB
PHP
<?php
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namespace Graphp\Algorithms;
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use Graphp\Algorithms\BaseGraph;
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use Fhaculty\Graph\Exception\UnexpectedValueException;
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use Fhaculty\Graph\Graph;
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use Fhaculty\Graph\Vertex;
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class Bipartit extends BaseGraph
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{
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/**
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* check whether this graph is bipartit
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*
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* @return boolean
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* @uses AlgorithmBipartit::getColors()
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*/
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public function isBipartit()
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{
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try {
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$this->getColors();
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return true;
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} catch (UnexpectedValueException $ignore) { }
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return false;
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}
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/**
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* checks whether the input graph's vertex groups are a valid bipartition
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*
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* @return boolean
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* @uses AlgorithmGroups::isBipartit()
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*/
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public function isBipartitGroups()
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{
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$alg = new Groups($this->graph);
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return $alg->isBipartit();
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}
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/**
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* get map of vertex ID to vertex color
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*
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* @return int[]
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* @throws UnexpectedValueException if graph is not bipartit
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* @uses AlgorithmBipartit::checkVertex() for every vertex not already colored
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*/
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public function getColors()
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{
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$colors = array();
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// get color for each vertex
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foreach ($this->graph->getVertices()->getMap() as $vid => $startVertex) {
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if (!isset($colors[$vid])) {
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$queue = array($startVertex);
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// initialize each components color
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$colors[$vid] = 0;
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// breadth search all vertices in same component
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do {
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// next vertex in color
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$vertex = array_shift($queue);
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$color = $colors[$vertex->getId()];
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$nextColor = 1-$color;
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// scan all vertices connected to this vertex
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foreach ($vertex->getVerticesEdge()->getMap() as $vid => $nextVertex) {
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// color unknown, so expect next color for this vertex
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if (!isset($colors[$vid])) {
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$colors[$vid] = $nextColor;
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$queue []= $nextVertex;
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// color is known but differs => can not be bipartit
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} elseif ($colors[$vid] !== $nextColor) {
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throw new UnexpectedValueException('Graph is not bipartit');
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}
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}
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} while ($queue);
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}
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}
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return $colors;
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}
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/**
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* get groups of vertices per color
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*
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* @return array[] array of arrays of vertices
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*/
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public function getColorVertices()
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{
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$colors = $this->getColors();
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$ret = array(0 => array(), 1 => array());
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foreach ($this->graph->getVertices()->getMap() as $vid => $vertex) {
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$ret[$colors[$vid]][$vid] = $vertex;
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}
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return $ret;
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}
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/**
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* create new graph with valid groups set according to bipartition colors
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*
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* @return Graph
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* @throws UnexpectedValueException if graph is not bipartit
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* @uses AlgorithmBipartit::getColors()
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* @uses Graph::createGraphClone()
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* @uses Vertex::setGroup()
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*/
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public function createGraphGroups()
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{
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$colors = $this->getColors();
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$graph = $this->graph->createGraphClone();
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foreach ($graph->getVertices()->getMap() as $vid => $vertex) {
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$vertex->setGroup($colors[$vid]);
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}
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return $graph;
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}
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}
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