Graph::UnionFind (3)
Leading comments
Automatically generated by Pod::Man 2.28 (Pod::Simple 3.28) Standard preamble: ========================================================================
NAME
Graph::UnionFind  unionfind data structuresSYNOPSIS
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.