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NAMEGraph::UnionFind - union-find data structures
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 )
DESCRIPTIONUnion-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().
Add the vertex v to the union-find.
Add the edge u-v to the union-find. Also implicitly adds the vertices.
Return true if the vertex v has been added to the union-find, false otherwise.
Return the union-find partition the vertex v belongs to, or "undef" if it has not been added.
$uf = Graph::UnionFind->new()
Return true of the vertices belong to the same union-find partition the vertex v belongs to, false otherwise.