| public static tarjan_scc ( Gliph\Graph\Digraph $graph, Gliph\Visitor\TarjanSCCVisitor $visitor = NULL ) : Gliph\Visitor\TarjanSCCVisitor | ||
| $graph | Gliph\Graph\Digraph | The Digraph to search for connected components. |
| $visitor | Gliph\Visitor\TarjanSCCVisitor | The visitor that will collect and store the connected components. One will be created if not provided. |
| return | Gliph\Visitor\TarjanSCCVisitor | The finalized visitor. |
public static function tarjan_scc(Digraph $graph, TarjanSCCVisitor $visitor = NULL)
{
$visitor = $visitor ?: new TarjanSCCVisitor();
$counter = 0;
$stack = array();
$indices = new \SplObjectStorage();
$lowlimits = new \SplObjectStorage();
$visit = function ($vertex) use(&$visit, &$counter, $graph, &$stack, $indices, $lowlimits, $visitor) {
$indices->attach($vertex, $counter);
$lowlimits->attach($vertex, $counter);
$stack[] = $vertex;
$counter++;
foreach ($graph->successorsOf($vertex) as $head) {
if (!$indices->contains($head)) {
$visit($head);
$lowlimits[$vertex] = min($lowlimits[$vertex], $lowlimits[$head]);
} else {
if (in_array($head, $stack, TRUE)) {
$lowlimits[$vertex] = min($lowlimits[$vertex], $indices[$head]);
}
}
}
if ($lowlimits[$vertex] === $indices[$vertex]) {
$visitor->newComponent();
do {
$other = array_pop($stack);
$visitor->addToCurrentComponent($other);
} while ($other != $vertex);
}
};
foreach ($graph->vertices() as $v) {
if (!$indices->contains($v)) {
$visit($v);
}
}
return $visitor;
} /**
* @covers \Gliph\Algorithm\ConnectedComponent::tarjan_scc()
*/
public function testTarjanScc()
{
$a = new TestVertex('a');
$b = new TestVertex('b');
$c = new TestVertex('c');
$d = new TestVertex('d');
$e = new TestVertex('e');
$f = new TestVertex('f');
$g = new TestVertex('g');
$h = new TestVertex('h');
$graph = new DirectedAdjacencyList();
$graph->addDirectedEdge($a, $d);
$graph->addDirectedEdge($a, $b);
$graph->addDirectedEdge($b, $c);
$graph->addDirectedEdge($c, $d);
$graph->addDirectedEdge($d, $a);
$graph->addDirectedEdge($e, $d);
$graph->addDirectedEdge($f, $g);
$graph->addDirectedEdge($g, $h);
$graph->addDirectedEdge($h, $f);
$visitor = ConnectedComponent::tarjan_scc($graph);
$expected_full = array(array($c, $b, $d, $a), array($e), array($h, $g, $f));
$this->assertEquals($expected_full, $visitor->getComponents());
$expected_full = array(array($c, $b, $d, $a), array($h, $g, $f));
$this->assertEquals($expected_full, $visitor->getConnectedComponents());
}