Graph::UnionFind(3pm)					User Contributed Perl Documentation				     Graph::UnionFind(3pm)

NAME

       Graph::UnionFind - union-find data structures

SYNOPSIS

	   use Graph::UnionFind;
	   my $uf = Graph::UnionFind->new;

	   # Add the vertices to the data structure.
	   $uf->add($u);
	   $uf->add($v);

	   # Join the partitions of the vertices.
	   $uf->union( $u, $v );

	   # Find the partitions the vertices belong to
	   # in the union-find data structure.	If they
	   # are equal, they are in the same partition.
	   # If the vertex has not been seen,
	   # undef is returned.
	   my $pu = $uf->find( $u );
	   my $pv = $uf->find( $v );
	   $uf->same($u, $v) # Equal to $pu eq $pv.

	   # Has the union-find seen this vertex?
	   $uf->has( $v )

DESCRIPTION

       Union-find is a special data structure that can be used to track the partitioning of a set into subsets (a problem known also as disjoint
       sets).

       Graph::UnionFind() is used for Graph::connected_components(), Graph::connected_component(), and Graph::same_connected_components() if you
       specify a true "union_find" parameter when you create an undirected graph.

       Note that union-find is one way: you cannot (easily) 'ununion' vertices once you have 'unioned' them.  This means that if you delete edges
       from a "union_find" graph, you will get wrong results from the Graph::connected_components(), Graph::connected_component(), and
       Graph::same_connected_components().

   API
       add
	       $uf->add($v)

	   Add the vertex v to the union-find.

       union
	       $uf->union($u, $v)

	   Add the edge u-v to the union-find.	Also implicitly adds the vertices.

       has
	       $uf->has($v)

	   Return true if the vertex v has been added to the union-find, false otherwise.

       find
	       $uf->find($v)

	   Return the union-find partition the vertex v belongs to, or "undef" if it has not been added.

       new
	       $uf = Graph::UnionFind->new()

	   The constructor.

       same
	       $uf->same($u, $v)

	   Return true of the vertices belong to the same union-find partition the vertex v belongs to, false otherwise.

AUTHOR AND COPYRIGHT

       Jarkko Hietaniemi jhi@iki.fi

LICENSE

       This module is licensed under the same terms as Perl itself.

perl v5.10.0							    2008-11-27						     Graph::UnionFind(3pm)