/**
* Constructs a PartitionTree
* for the specified element of the universal set
* a the specified Partition.
*
* @param object PartitionAsForest $partition The partition.
* @param integer $item An element of the universal set.
*/
public function __construct(PartitionAsForest $partition, $item)
{
parent::__construct($partition->getUniverseSize());
$this->partition = $partition;
$this->item = $item;
$this->parent = NULL;
$this->rank = 0;
$this->count = 1;
}
/**
* Main program.
*
* @param array $args Command-line arguments.
* @return integer Zero on succes; non-zero on failure.
*/
public static function main($args)
{
printf("Demonstration program number 7.\n");
$status = 0;
SetAsArray::main($args);
SetAsBitVector::main($args);
MultisetAsArray::main($args);
MultisetAsLinkedList::main($args);
PartitionAsForest::main($args);
return $status;
}
/**
* Destructor.
*/
public function __destruct()
{
parent::__destruct();
}
/**
* Kruskal's algorithm to find a minimum-cost spanning tree
* for the given edge-weighted, undirected graph.
* Uses a partition and a priority queue.
*
* @param object IGraph $g An edge-weighted, undirected graph.
* It is assumed that the edge weights are <code>Int</code>s
* @return object IGraph An unweighted, undirected graph that represents
* the minimum-cost spanning tree.
*/
public static function kruskalsAlgorithm(IGraph $g)
{
$n = $g->getNumberOfVertices();
$result = new GraphAsLists($n);
for ($v = 0; $v < $n; ++$v) {
$result->addVertex($v);
}
$queue = new BinaryHeap($g->getNumberOfEdges());
foreach ($g->getEdges() as $edge) {
$weight = $edge->getWeight();
$queue->enqueue(new Association($weight, $edge));
}
$partition = new PartitionAsForest($n);
while (!$queue->isEmpty() && $partition->getCount() > 1) {
$assoc = $queue->dequeueMin();
$edge = $assoc->getValue();
$n0 = $edge->getV0()->getNumber();
$n1 = $edge->getV1()->getNumber();
$s = $partition->findItem($n0);
$t = $partition->findItem($n1);
if ($s !== $t) {
$partition->join($s, $t);
$result->addEdge($n0, $n1);
}
}
return $result;
}
throw new MethodNotImplemented();
}
/**
* Compares this partition with the specified comparable object.
* This method is not implemented.
*
* @param object IComparable $obj
* The object with which this partition is compared.
*/
protected function compareTo(IComparable $arg)
{
throw new MethodNotImplemented();
}
/**
* Main program.
*
* @param array $args Command-line arguments.
* @return integer Zero on success; non-zero on failure.
*/
public static function main($args)
{
printf("PartitionAsForest main program.\n");
$status = 0;
$p = new PartitionAsForest(5);
AbstractPartition::test($p);
return $status;
}
}
if (realpath($argv[0]) == realpath(__FILE__)) {
exit(PartitionAsForest::main(array_slice($argv, 1)));
}
