/**
* check whether this graph has an eulerian cycle
*
* @return boolean
* @uses ConnectedComponents::isSingle()
* @uses Degree::getDegreeVertex()
* @todo isolated vertices should be ignored
* @todo definition is only valid for undirected graphs
*/
public function hasCycle()
{
$components = new ConnectedComponents($this->graph);
if ($components->isSingle()) {
$alg = new Degree($this->graph);
foreach ($this->graph->getVertices() as $vertex) {
// uneven degree => fail
if ($alg->getDegreeVertex($vertex) & 1) {
return false;
}
}
return true;
}
return false;
}
public function testComponents()
{
// 1 -- 2, 3 -> 4, 5
$graph = new Graph();
$v1 = $graph->createVertex(1);
$v2 = $graph->createVertex(2);
$v3 = $graph->createVertex(3);
$v4 = $graph->createVertex(4);
$v5 = $graph->createVertex(5);
$e1 = $v1->createEdge($v2);
$e2 = $v3->createEdgeTo($v4);
$alg = new AlgorithmConnected($graph);
$this->assertEquals(3, $alg->getNumberOfComponents());
$this->assertFalse($alg->isSingle());
$graphs = $alg->createGraphsComponents();
$this->assertCount(3, $graphs);
$ge = new Graph();
$ge->createVertex(1)->createEdge($ge->createVertex(2));
$this->assertGraphEquals($ge, $alg->createGraphComponentVertex($v2));
$ge = new Graph();
$ge->createVertex(5);
$this->assertEquals($ge, $alg->createGraphComponentVertex($v5));
}