94 lines
2.4 KiB
PHP
94 lines
2.4 KiB
PHP
<?php
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namespace Graphp\Algorithms\TravelingSalesmanProblem;
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use Fhaculty\Graph\Exception\UnexpectedValueException;
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use Fhaculty\Graph\Vertex;
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use Fhaculty\Graph\Edge\Base as Edge;
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use Fhaculty\Graph\Set\Edges;
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use \SplPriorityQueue;
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class NearestNeighbor extends Base4
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{
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/**
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*
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* @var Vertex
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*/
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private $vertex;
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public function __construct(Vertex $startVertex)
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{
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$this->vertex = $startVertex;
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}
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protected function getVertexStart()
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{
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return $this->vertex;
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}
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protected function getGraph()
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{
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return $this->vertex->getGraph();
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}
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/**
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*
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* @return Edges
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*/
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public function getEdges()
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{
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$returnEdges = array();
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$n = count($this->vertex->getGraph()->getVertices());
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$vertex = $this->vertex;
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$visitedVertices = array($vertex->getId() => true);
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for ($i = 0; $i < $n - 1; ++$i,
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// n-1 steps (spanning tree)
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$vertex = $nextVertex) {
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// get all edges from the aktuel vertex
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$edges = $vertex->getEdgesOut();
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$sortedEdges = new SplPriorityQueue();
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// sort the edges
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foreach ($edges as $edge) {
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$sortedEdges->insert($edge, - $edge->getWeight());
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}
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// Untill first is found: get cheepest edge
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foreach ($sortedEdges as $edge) {
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// Get EndVertex of this edge
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$nextVertex = $edge->getVertexToFrom($vertex);
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// is unvisited
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if (!isset($visitedVertices[$nextVertex->getId()])) {
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break;
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}
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}
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// check if there is a way i can use
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if (isset($visitedVertices[$nextVertex->getId()])) {
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throw new UnexpectedValueException('Graph is not complete - can\'t find an edge to unconnected vertex');
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}
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$visitedVertices[$nextVertex->getId()] = TRUE;
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// clone edge in new Graph
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$returnEdges []= $edge;
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}
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// check if there is a way from end edge to start edge
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// get first connecting edge
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// connect the last vertex with the start vertex
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$returnEdges []= $vertex->getEdgesTo($this->vertex)->getEdgeFirst();
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return new Edges($returnEdges);
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}
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}
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