Good day.

I am working on a problem that is just an intellectual challenge. I am not asking for help on solving the actual problem, rather just help on optimizing a loop. As it stands, running the script over the input takes a few hours to complete.

After the initial loading the array @input_connections, will contain pairs of numbers where each element is in a format like '7-12' (starting connection-ending connection). The code snippet below reads through each of these pairs and culls out the ones that are already implied by the other pairs

Whereas if the pair '7-12' was stored and the next pair is '7-10', '7-10' would be rejected because '7-10' falls within the range of '7-12'.

The array @used_connections stores numbers that have been used in each pair. The array @output_connections stores the connections that are to be output from the processing.

Ideally, I'd love to have the connections stored in a hash and be able to check for used numbers with something like ' if exists $hash{key1...keyN} ' thereby removing a loop for checking. I am seeking wisdom to see if there is ( and I am sure there is ) a more efficient way to go about this part.

Any suggestions will be most appreciated. Thanks!

I apologize if this does not make sense.

Code snippet

###############################################################
my $pair_no = 1;

foreach my $conn (@input_connections)
{
    print "\rON pair $pair_no";
    my @curr_conn = split(/\-/,$conn);
    
    ## check if current connection exists

    my $exists = 1;

    my $start  = $curr_conn[0];
    my $end    = $curr_conn[1];

    ## first number in pair is larger than second, reverse them
    if ($curr_conn[0] > $curr_conn[1])
    {
        $start = $curr_conn[1];
        $end   = $curr_conn[0];
    }

    ## ** Ideally I want to do away with this loop ** ##
    for ($start..$end)
    {
        if ( not defined $used_connections[$_] )
        {
            $exists = 0;
            last;
        }
    }

    if ($exists == 0)
    {
        for ($start..$end)
        {
            $used_connections[$_] = 1;
            
            # I tried something like @used_connections[$start..$end] =
+ 1 , but
            # it did not seem to work the same as what is in place now
+.
        }
        push @output_connections , $conn;
    }
    $pair_no++;
}
###############################################################

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In reply to Request help on optimizing a loop for looking up numbers by VincentK

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