Current File : /home/tjamichg/cursos.tjamich.gob.mx/vendor/graphp/algorithms/src/TopologicalSort.php
<?php
namespace Graphp\Algorithms;
use Fhaculty\Graph\Exception\UnexpectedValueException;
use Fhaculty\Graph\Set\Vertices;
use Fhaculty\Graph\Vertex;
/**
* topological sorting / order, also known as toposort / topsort, commonly used in resolving dependencies
*
* @author clue
* @link http://en.wikipedia.org/wiki/Topological_sorting
*/
class TopologicalSort extends BaseGraph
{
/**
* run algorithm and return an ordered/sorted set of Vertices
*
* the topological sorting may be non-unique depending on your edges
*
* @return Vertices
*/
public function getVertices()
{
$stack = array(); // visited nodes with unvisited children
$visited = array();
$output = array();
// TODO: avoid having to reverse all vertices multiple times
// pick a node to examine next - assume there are isolated nodes
foreach (\array_reverse($this->graph->getVertices()->getVector()) as $top) {
assert($top instanceof Vertex);
$tid = $top->getId();
if (!isset($visited[$tid])) { // don't examine if already found
\array_push($stack, $top);
}
while ($stack) {
$node = \end($stack);
assert($node instanceof Vertex);
$nid = $node->getId();
$visited[$nid] = false; // temporary mark
$found = false; // new children found during visit to this node
// find the next node to visit
foreach (\array_reverse($node->getVerticesEdgeTo()->getVector()) as $child) {
assert($child instanceof Vertex);
$cid = $child->getId();
if (!isset($visited[$cid])) {
// found a new node - push it onto the stack
\array_push($stack, $child);
$found = true; // move onto the new node
break;
} else if ($visited[$cid] === false) {
// temporary mark => not a DAG
throw new UnexpectedValueException('Not a DAG');
}
}
if (!$found) {
\array_pop($stack); // no new children found - we're done with this node
$visited[$nid] = true; // mark as visited
\array_push($output, $node); // add to results
}
}
}
return new Vertices(\array_reverse($output, true));
}
}
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