Re: pattern finding problem

I haven't yet had the chance to thoroughly test and Benchmark this vs. 
Ron Kimball's solution, so there's no summary yet to report (beside the 
fact that you and Ron Kimball both provided apparently reasonable 
solutions).  I will also, as originally promised, package the "winning" 
solution into BioPerl's Bio::Tools::* namespace for general biosequence 
pattern matching.  But not today, and probably not tomorrow.  Beyond 
that, I cannot say.

-Aaron

On Mar 17, 2004, at 5:51 PM, John Douglas Porter wrote:

>
> Here's my solution, which I sent to the OP off list.
> Funny how he never reported back with a summary, as
> is the custom....
>
>
>   # operates on $_
>   sub find_subsequences
>   {
>     #local $_ = shift; # if you'd rather pass it.
>     my( $chars, $min_occurrences, $max_subseq_length, $results_ar ) =
> @_;
>     $results_ar ||= [];
>     my @p; # a sliding window of positions at which pattern matches.
>     while ( /[$chars]/g )
>     {
>       push @p, pos() - 1; # since pos() is 1-based.
>       shift @p while @p > $min_occurrences; # slide the window
>       if ( @p == $min_occurrences )
>       {
>         my $len = $p[-1] - $p[0] + 1;
>         if ( $len <= $max_subseq_length )
>         {
>           my $subseq = substr $_, $p[0], $len;
>           push @$results_ar, [ $p[0], $subseq ];
>         }
>       }
>     }
>     $results_ar
>   }
>
>
>   # test
>
>   my @chars = qw( A T C G );
>
>   $_ = '';
>   for ( my $i = 0; $i < 10_000; $i++ )
>   {
>     $_ .= $chars[ rand @chars ];
>   }
>
>     use Tie::Array;
>     @Tie::ArrayPrint::ISA = qw( Tie::StdArray );
>     sub Tie::ArrayPrint::PUSH
>     {
>       my $self = shift;
>       @_ == 1 && ref($_[0]) eq 'ARRAY' and
>         print "\@ $_[0][0] ($_[0][1])\n";
>       push @$self, @_;
>     }
>
>   my @subseqs;
>   #tie @subseqs, 'Tie::ArrayPrint';
>   find_subsequences( join('',@chars[0,1]), 7, 12, \@subseqs );
>   print scalar(@subseqs), " hits found.\n";
>
>
> -- 
> John Douglas Porter
>
>
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