/**
*
* @param Vertex $vertex current point-of-view
* @param number $totalWeight total weight (so far)
* @param boolean[] $visitedVertices
* @param Edge[] $visitedEdges
* @return Edge[]
*/
private function step(Vertex $vertex, $totalWeight, array $visitedVertices, array $visitedEdges)
{
// stop recursion if best result is exceeded (branch and bound)
if ($this->branchAndBound && $this->bestWeight !== NULL && $totalWeight >= $this->bestWeight) {
return NULL;
}
// kreis geschlossen am Ende
if ($vertex === $this->startVertex && count($visitedEdges) === $this->numEdges) {
// new best result
$this->bestWeight = $totalWeight;
return $visitedEdges;
}
// only visit each vertex once
if (isset($visitedVertices[$vertex->getId()])) {
return NULL;
}
$visitedVertices[$vertex->getId()] = true;
$bestResult = NULL;
// weiter verzweigen in alle vertices
foreach ($vertex->getEdgesOut() as $edge) {
// get target vertex of this edge
$target = $edge->getVertexToFrom($vertex);
$weight = $edge->getWeight();
if ($weight < 0) {
throw new UnexpectedValueException('Edge with negative weight "' . $weight . '" not supported');
}
$result = $this->step($target, $totalWeight + $weight, $visitedVertices, array_merge($visitedEdges, array($edge)));
// new result found
if ($result !== NULL) {
// branch and bound enabled (default): returned result MUST be the new best result
if ($this->branchAndBound || $bestResult === NULL || $this->sumEdges($result) < $this->sumEdges($bestResult)) {
$bestResult = $result;
}
}
}
return $bestResult;
}
