Hi,

I really don't know what are your nodes, and when they disconnect from others

With your example data, you can simplify to:

use strict;
use warnings;

my $queryCount=0;
my $answeredCount=0;
my %connected=();
while(<>)
{
    print;
    chomp($_);
    if (/q (\d+) (\d+)/)
    {
        $answeredCount++ if ( defined $connected{$1} and $connected{$2
+});
        $queryCount++;
    }
    elsif (/c (\d+) (\d+)/)
    {
        $connected{$1}=1;
        $connected{$2}=1;
    }
}

print "$answeredCount,".($queryCount-$answeredCount)."\n";
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I suspect you should use a hash more complex may be:

$connected{firstSet}{$n1}=1; # or better $connected{1}{x}=1;
$connected{secondSet}{$n1}=1; # or better $connected{2}{x}=1;
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And detect when you have to delete one node from connected in the correspondient set (delete $connected{x}{N})

I hope that help, be sure to read perldata

Regards,