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<?php |
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namespace Sugarcrm\UpgradeSpec\Version\Graph; |
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use Sugarcrm\UpgradeSpec\Version\Version; |
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class Dijkstra |
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{ |
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/** |
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* @var array |
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*/ |
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private $graph; |
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/** |
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* Graph constructor. |
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* |
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* @param AdjacencyList $adj |
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*/ |
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public function __construct(AdjacencyList $adj) |
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{ |
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foreach ($adj as $vertex => $list) { |
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$list = array_map(function (Version $version) use ($vertex) { |
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return [(string) $version => (new Version($vertex))->isChildOf($version) ? 0 : 1]; |
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}, iterator_to_array($list)); |
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$this->graph[(string) $vertex] = $list ? call_user_func_array('array_merge', $list) : []; |
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} |
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} |
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/** |
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* @param Version $from |
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* @param Version $to |
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* |
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* @return array |
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*/ |
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public function getPath(Version $from, Version $to) |
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{ |
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$destinations = $this->getDestinationVertexes($to); |
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foreach ($this->getOriginVertexes($from) as $origin) { |
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foreach ($destinations as $destination) { |
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if ($path = $this->getShortestPath((string) $origin, (string) $destination)) { |
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return $this->getRealHops($path); |
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} |
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} |
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} |
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return []; |
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} |
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/** |
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* @param $path |
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* |
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* @return array |
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*/ |
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private function getRealHops($path) |
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{ |
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$pairs = []; |
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$first = new Version($path[0]); |
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foreach (range(1, count($path) - 1) as $index) { |
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$second = new Version($path[$index]); |
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if ($first->isChildOf($second)) { |
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$first = $second; |
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continue; |
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} |
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$pairs[] = [$first, $second]; |
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$first = $second; |
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} |
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return $pairs; |
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} |
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private function getShortestPath($source, $target) |
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{ |
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// array of the best estimates of shortest path to each vertex |
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$bestEstimates = []; |
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// array of predecessors for each vertex |
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$predecessors = []; |
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// queue of all unoptimized vertices |
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$queue = new \SplPriorityQueue(); |
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foreach ($this->graph as $vertex => $list) { |
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$bestEstimates[$vertex] = \INF; // set initial distance to "infinity" |
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$predecessors[$vertex] = null; // no known predecessors yet |
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foreach ($list as $w => $cost) { |
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// use the edge cost as the priority |
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$queue->insert($w, $cost); |
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} |
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} |
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// initial distance at source is 0 |
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$bestEstimates[$source] = 0; |
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while (!$queue->isEmpty()) { |
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// extract min cost |
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$u = $queue->extract(); |
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if (!empty($this->graph[$u])) { |
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// "relax" each adjacent vertex |
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foreach ($this->graph[$u] as $vertex => $cost) { |
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// alternate route length to adjacent neighbor |
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$alt = $bestEstimates[$u] + $cost; |
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/** |
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* if alternate route is shorter: |
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* - update minimum length to vertex |
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* - add neighbor to predecessors for vertex |
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*/ |
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if ($alt < $bestEstimates[$vertex]) { |
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$bestEstimates[$vertex] = $alt; |
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$predecessors[$vertex] = $u; |
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$queue->insert($vertex, $cost); |
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} |
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} |
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} |
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} |
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// we can now find the shortest path using reverse iteration |
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$path = []; |
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$u = $target; |
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while (isset($predecessors[$u]) && $predecessors[$u]) { |
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$path[] = $u; |
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$u = $predecessors[$u]; |
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} |
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if (!$path) { |
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return []; |
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} |
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return array_reverse(array_merge($path, [$source])); |
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} |
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/** |
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* @param Version $from |
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* |
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* @return OrderedList |
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*/ |
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private function getOriginVertexes(Version $from) |
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{ |
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$aliases = $from->getAliases(); |
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while ($from->isMinor()) { |
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$from = $from->getParent(); |
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$aliases = $aliases->merge($from->getAliases()); |
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} |
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return $aliases->filter(function (Version $version) { |
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return isset($this->graph[(string) $version]); |
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}); |
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} |
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/** |
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* @param Version $to |
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* |
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* @return OrderedList |
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*/ |
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private function getDestinationVertexes(Version $to) |
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{ |
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return $to->getAliases()->filter(function (Version $version) { |
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return isset($this->graph[(string) $version]); |
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}); |
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} |
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} |
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mikekamornikov /
UpgradeSpec
Loading history...
This check marks implicit conversions of arrays to boolean values in a comparison. While in PHP an empty array is considered to be equal (but not identical) to false, this is not always apparent.
Consider making the comparison explicit by using
empty(..)or! empty(...)instead.