Dear Monks,

Thank you very much every one. I didn't expect this many replies.

=>Ram:By Linear time I means O(n), which deals with time complexity.

=>BrowserUK & AnomalousMonk:Thank you very much guys that was a very gud kick start.

So as BrowseUK and AnomalousMonk suggested I have attached the script, which I have modified as per the requirements but the problem with this is it took 3mins to run on a file sized only 7 MB. this is not efficient as I have to deal with file sized over GB's. So now how do I optimize it for file sized over GB's or is there any other efficient way to accomplished this.

Note: I have noticed that using an array slows down the run time.Isn't much a big discovery, but can we use any alternate.


use List::MoreUtils qw(uniq);

open(HD,"File") or die ("Cant open");
$text=<HD>;
chomp $text;

my $n    = 6;
my $back = $n - 1;
my @array = unpack qq{(a$n X$back)*}, $text;

@unpacked=uniq @array;

for($i=0;$i<=$#unpacked-$back;$i++)
{
    $pattern= $unpacked[$i];
    $offset = 0;
    print "\n$pattern ($n)\n";
    print '~' x $n,"\n";
    
    $pos=index $text,$pattern,$offset;

    while ($pos != -1) 
    {    
        print $pos+1," to ",$pos+$n,"\n";
        $offset = $pos + 1;
        $pos = index($text, $pattern, $offset);
    }
}

[download]

In reply to Re: Exact string matching by saranrsm
in thread Exact string matching by Anonymous Monk

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