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<?php |
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namespace TemplesOfCode\NodesAndEdges\DFS; |
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use TemplesOfCode\NodesAndEdges\Digraph; |
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use TemplesOfCode\NodesAndEdges\Graph; |
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/** |
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* Class DSCC |
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* |
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* API for Directed Graph Strongly Connected Components |
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* |
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* @package TemplesOfCode\NodesAndEdges\DFS |
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*/ |
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class DSCC extends ConnectedComponent |
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{ |
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/** |
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* Computes the connected components of the undirected graph g. |
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* |
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* @param Digraph $g the graph |
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*/ |
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public function __construct(Digraph $g) |
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{ |
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// init |
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$this->count = 0; |
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// get vertices |
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$vertices = $g->getVertices(); |
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// set |
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$this->graph = $g; |
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// init |
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$this->marked = array_fill(0, $vertices, false); |
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// init |
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$this->id = array_fill(0, $vertices, null); |
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// build a dfo |
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$dfo = new DepthFirstOrder($g->reverse()); |
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// get the order |
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$reversePostorder = $dfo->reversePostorder(); |
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// iterate over the set |
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foreach ($reversePostorder as $s) { |
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// check if we have touched this vertex |
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if (!$this->marked[$s]) { |
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// run it |
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$this->dfs($s); |
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// increment the count for components |
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$this->count++; |
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} |
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} |
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} |
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/** |
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* @param int $v |
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* @param int $w |
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* @return bool |
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*/ |
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public function stronglyConnected(int $v, int $w) |
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{ |
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// delegate to default |
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return $this->connected($v, $w); |
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} |
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/** |
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* Depth-first search for an DirectedGraph |
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* @param int $vertex |
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*/ |
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protected function dfs(int $vertex) |
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{ |
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// we have visited now |
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$this->marked[$vertex] = true; |
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// set the component # |
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$this->id[$vertex] = $this->count; |
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// get the neighbors |
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$neighbors = $this->graph->adjacent($vertex); |
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// iterate over the neighbors |
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foreach ($neighbors as $w) { |
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// check if we have visited |
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if (!$this->marked[$w]) { |
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// lets visit |
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$this->dfs($w); |
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} |
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} |
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} |
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} |
templesofcode /
nodes-and-edges
