NAME
Graph::UnionFind  unionfind 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 unionfind 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 unionfind seen this vertex?
$uf>has( $v )
DESCRIPTION
Unionfind 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 unionfind 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 unionfind.
 union

$uf>union($u, $v)
Add the edge uv to the unionfind. Also implicitly adds the vertices.
 has

$uf>has($v)
Return true if the vertex v has been added to the unionfind, false otherwise.
 find

$uf>find($v)
Return the unionfind 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 unionfind 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.