http://www.perlmonks.org?node_id=898542


in reply to Re: how to find combine common elements of an array?
in thread how to find combine common elements of an array?

Here's a better version. I was going to wipe my scratchpad and saw that I could do one thing better ... then another ... then realized that there didn't need to be an identified element per subgraph...

#!/usr/bin/env perl use strict; use warnings; use List::MoreUtils(qw(uniq)); my @array = map {[split]} ("11 12", "11 13", "9 8 7", "3 4", "11 4"); my %g = (); for my $i (@array) { my @v = map {@$_} uniq map {$g{$_} or [$_]} @$i; @g{@v} = (\@v) x @v; } print join ("\n", map {join " ", sort {$a<=>$b} @$_} uniq values %g), +"\n";

Same output as above, although now the ordering of the lines is fortuitous. (But obviously can be set, if desired, by another sort.)

Hopefully it's a bit more clear that, since each iteration creates a complete set of associated vertices, the process finds the sets of vertices of the connected subgraphs of an arbitrary graph.

(Please pardon the enthusiasm, this is the kind of stuff I like to think about.)