#!/usr/bin/env perl

use strict;
use warnings;
use List::Util(qw(min));
use List::MoreUtils(qw(uniq));

my @array = map {[split]} ("11 12", "11 13", "9 8 7", "3 4", "11 4");

my %v2g = ();
my %g2v = ();

for my $i (@array) {
    my @sg = sort {$a<=>$b} uniq grep {defined} (@v2g{@$i}, min @$i);
    my $sg = shift @sg;
    $g2v{$v2g{$_} ||= $sg}->{$_}++ for @$i;
    for my $j (@sg) {
        @v2g{keys %{$g2v{$j}}} = ($sg) x keys %{$g2v{$j}};
        @{$g2v{$sg}}{keys %{$g2v{$j}}} = values %{$g2v{$j}};
        delete $g2v{$j};
    }
}

print join ("\n", map {join " ", sort {$a<=>$b} keys %$_} values %g2v), "\n";