Current File : /home/tjamichg/cursos.tjamich.gob.mx/vendor/graphp/algorithms/src/ConnectedComponents.php
<?php
namespace Graphp\Algorithms;
use Fhaculty\Graph\Exception\InvalidArgumentException;
use Fhaculty\Graph\Exception\UnderflowException;
use Fhaculty\Graph\Graph;
use Fhaculty\Graph\Vertex;
use Graphp\Algorithms\Search\BreadthFirst as SearchBreadthFirst;
/**
* Algorithm for working with connected components
*
* @link http://en.wikipedia.org/wiki/Connected_component_%28graph_theory%29
* @link http://mathworld.wolfram.com/ConnectedGraph.html
* @link http://math.stackexchange.com/questions/50551/is-the-empty-graph-connected
*/
class ConnectedComponents extends BaseGraph
{
/**
* create subgraph with all vertices connected to given vertex (i.e. the connected component of ths given vertex)
*
* @param Vertex $vertex
* @return Graph
* @throws InvalidArgumentException if given vertex is not from same graph
* @uses AlgorithmSearchBreadthFirst::getVertices()
* @uses Graph::createGraphCloneVertices()
*/
public function createGraphComponentVertex(Vertex $vertex)
{
if ($vertex->getGraph() !== $this->graph) {
throw new InvalidArgumentException('This graph does not contain the given vertex');
}
return $this->graph->createGraphCloneVertices($this->createSearch($vertex)->getVertices());
}
/**
*
* @param Vertex $vertex
* @return SearchBreadthFirst
*/
private function createSearch(Vertex $vertex)
{
$alg = new SearchBreadthFirst($vertex);
// follow into both directions (loosely connected)
return $alg->setDirection(SearchBreadthFirst::DIRECTION_BOTH);
}
/**
* check whether this graph consists of only a single component
*
* If a Graph consists of only a single component, it is said to be a
* connected Graph, otherwise it's called a disconnected Graph.
*
* This method returns exactly the same result as checking
* <pre>($this->getNumberOfComponents() === 1)</pre>. However, using this
* method is faster than calling getNumberOfComponents(), as it only has to
* count all vertices in one component to see if the graph consists of only
* a single component.
*
* As such, a null Graph (a Graph with no vertices) is not considered
* connected here.
*
* @return bool
* @see self::getNumberOfComponents()
*/
public function isSingle()
{
try {
$vertex = $this->graph->getVertices()->getVertexFirst();
} catch (UnderflowException $e) {
// no first vertex => empty graph => has zero components
return false;
}
$alg = $this->createSearch($vertex);
return (\count($this->graph->getVertices()) === \count($alg->getVertices()));
}
/**
* count number of connected components
*
* A null Graph (a Graph with no vertices) will return 0 components.
*
* @return int number of components
* @uses Graph::getVertices()
* @uses AlgorithmSearchBreadthFirst::getVertices()
*/
public function getNumberOfComponents()
{
$visitedVertices = array();
$components = 0;
// for each vertices
foreach ($this->graph->getVertices()->getMap() as $vid => $vertex) {
// did I visit this vertex before?
if (!isset($visitedVertices[$vid])) {
// get all vertices of this component
$newVertices = $this->createSearch($vertex)->getVertices()->getIds();
++$components;
// mark the vertices of this component as visited
foreach ($newVertices as $vid) {
$visitedVertices[$vid] = true;
}
}
}
// return number of components
return $components;
}
/**
* separate input graph into separate independant and unconnected graphs
*
* @return Graph[]
* @uses Graph::getVertices()
* @uses AlgorithmSearchBreadthFirst::getVertices()
*/
public function createGraphsComponents()
{
$visitedVertices = array();
$graphs = array();
// for each vertices
foreach ($this->graph->getVertices()->getMap() as $vid => $vertex) {
// did I visit this vertex before?
if (!isset($visitedVertices[$vid])) {
$alg = $this->createSearch($vertex);
// get all vertices of this component
$newVertices = $alg->getVertices();
// mark the vertices of this component as visited
foreach ($newVertices->getIds() as $vid) {
$visitedVertices[$vid] = true;
}
$graphs[] = $this->graph->createGraphCloneVertices($newVertices);
}
}
return $graphs;
}
}
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