45 lines
1.3 KiB
PHP
45 lines
1.3 KiB
PHP
<?php
|
|
|
|
namespace Graphp\Algorithms;
|
|
|
|
use Graphp\Algorithms\BaseGraph;
|
|
use Fhaculty\Graph\Edge\Directed as EdgeDirected;
|
|
use Fhaculty\Graph\Graph;
|
|
use Fhaculty\Graph\Vertex;
|
|
|
|
/**
|
|
* Basic algorithms for working with symmetric digraphs
|
|
*
|
|
* A directed graph is called symmetric if, for every arc that belongs to it,
|
|
* the corresponding reversed arc (antiparallel directed edge) also belongs to it.
|
|
*
|
|
* @link http://en.wikipedia.org/wiki/Directed_graph#Classes_of_digraphs
|
|
*/
|
|
class Symmetric extends BaseGraph
|
|
{
|
|
/**
|
|
* checks whether this graph is symmetric (for every edge a->b there's also an edge b->a)
|
|
*
|
|
* @return boolean
|
|
* @uses Graph::getEdges()
|
|
* @uses EdgeDirected::getVertexStart()
|
|
* @uses EdgeDirected::getVertedEnd()
|
|
* @uses Vertex::hasEdgeTo()
|
|
*/
|
|
public function isSymmetric()
|
|
{
|
|
// check all edges
|
|
foreach ($this->graph->getEdges() as $edge) {
|
|
// only check directed edges (undirected ones are symmetric by definition)
|
|
if ($edge instanceof EdgeDirected) {
|
|
// check if end also has an edge to start
|
|
if (!$edge->getVertexEnd()->hasEdgeTo($edge->getVertexStart())) {
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
}
|