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<?php |
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namespace TemplesOfCode\NodesAndEdges\DFS; |
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use InvalidArgumentException; |
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use TemplesOfCode\NodesAndEdges\Graph; |
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/** |
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* Class ConnectedComponent |
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* @package TemplesOfCode\NodesAndEdges\DFS |
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*/ |
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abstract class ConnectedComponent |
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{ |
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/** |
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* id[v] = id of connected component containing v |
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* |
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* @var int[] |
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*/ |
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protected $id; |
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/** |
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* marked[v] = has vertex v been marked? |
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* |
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* @var bool[] |
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*/ |
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protected $marked; |
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/** |
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* size[id] = number of vertices in given component |
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* |
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* @var int[] |
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*/ |
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protected $size; |
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/** |
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* number of connected components |
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* |
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* @var int |
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*/ |
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protected $count; |
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/** |
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* @var Graph |
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*/ |
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protected $graph; |
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/** |
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* Computes the connected components of the graph g. |
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* |
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* @param Graph $g the graph |
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*/ |
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public function __construct(Graph $g) |
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{ |
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// set |
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$this->graph = $g; |
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// get vertices |
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$vertices = $g->getVertices(); |
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// init |
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$this->marked = array_fill(0, $vertices, false); |
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// init |
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$this->id = array_fill(0, $vertices, 0); |
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// init |
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$this->size = array_fill(0, $vertices, 0); |
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// init |
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$this->count = 0; |
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// iterate over the set |
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for ($vertex = 0; $vertex < $vertices; $vertex++) { |
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// check if we have touched this vertex |
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if (!$this->marked[$vertex]) { |
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// we haven't, lets explore |
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$this->dfs($vertex); |
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// increment the count for components |
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$this->count++; |
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} |
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} |
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} |
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/** |
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* Returns the component id of the connected component containing vertex $v. |
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* |
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* @param int $v the vertex |
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* @return int the component id of the connected component containing vertex $v |
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* @throws InvalidArgumentException unless 0 <= $v < V |
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*/ |
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public function id(int $v) |
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{ |
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// validate |
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Graph::validateVertex($v, $this->graph->getVertices()); |
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// fetch and return |
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return $this->id[$v]; |
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} |
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/** |
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* Returns the number of vertices in the connected component containing $v |
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* |
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* @param int $v the vertex |
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* @return int the number of vertices in the connected component containing $v |
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* @throws InvalidArgumentException unless 0 <= v < V |
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*/ |
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public function size(int $v) |
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{ |
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// validate |
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Graph::validateVertex($v, $this->graph->getVertices()); |
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// fetch and return |
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return $this->size[$this->id($v)]; |
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} |
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/** |
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* Returns the number of connected components in the graph |
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* |
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* @return int the number of connected components in the graph |
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*/ |
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public function count() |
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{ |
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// fetch and return |
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return $this->count; |
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} |
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/** |
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* Returns true if vertices $v and $w are in the same |
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* connected component. |
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* |
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* @param int $v one vertex |
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* @param int $w the other vertex |
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* @return bool true if vertices v and w are in the same |
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* connected component; false otherwise |
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* @throws InvalidArgumentException unless 0 <= v < V |
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* @throws InvalidArgumentException unless 0 <= w < V |
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*/ |
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public function connected(int $v, int $w) |
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{ |
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// validate |
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Graph::validateVertex($v, $this->graph->getVertices()); |
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// validate |
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Graph::validateVertex($w, $this->graph->getVertices()); |
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// evaluate |
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return $this->id($v) == $this->id($w); |
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} |
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/** |
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* Is there a path between the source vertex and vertex v |
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* |
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* @param int $vertex |
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* @return bool true if there is a path, false otherwise |
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* @throws InvalidArgumentException unless 0 <= $vertex < $vertices |
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*/ |
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public function marked(int $vertex) |
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{ |
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// convenience var |
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$vertices = $this->graph->getVertices(); |
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// validate this vertex in the context of the given graph |
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Graph::validateVertex($vertex, $vertices); |
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// return the flag |
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return $this->marked[$vertex]; |
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} |
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/** |
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* @param int $vertex |
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* @return mixed |
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*/ |
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abstract protected function dfs(int $vertex); |
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} |
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templesofcode /
nodes-and-edges
