Beefy Boxes and Bandwidth Generously Provided by pair Networks
good chemistry is complicated,
and a little bit messy -LW
 
PerlMonks  

Re: "Inverse" Pattern Matching

by choroba (Cardinal)
on Jul 04, 2013 at 22:32 UTC ( [id://1042533]=note: print w/replies, xml ) Need Help??


in reply to "Inverse" Pattern Matching

What about this? I keep a list of possible positions, I delete non-matching positions recursively character by character. If I make the string much longer (x 100_000), it still runs only for 8 seconds on my box.
#!/usr/bin/perl use warnings; use strict; use feature qw(say); # 1 2 3 4 # 0123456789012345678901234567890123456789012345 # | | | | | | our $string = '1234561234123x561234123x61234x3456123412345x1'; our $pattern = '123456'; our $pattern_length = length $pattern; our %results; search(0, 0, [0 .. length($string) - 1]); say for sort { $a <=> $b } keys %results; sub search { my ($p_pos, $s_pos, $positions) = @_; return if $p_pos > $pattern_length; return unless @$positions; if ($p_pos == $pattern_length) { undef @results{@$positions}; return; } my $char = substr $pattern, $p_pos, 1; search($p_pos + 1, $s_pos + 1, [ grep { my $ch = substr($string, $s_pos + $_, 1); $char eq $ch or 'x' eq $ch; } @$positions ]); search($p_pos + 2, $s_pos + 1, [ grep substr($string, $s_pos + $_, 1) eq 'x', @$positions ]); }
لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

Replies are listed 'Best First'.
Re^2: "Inverse" Pattern Matching
by hdb (Monsignor) on Jul 05, 2013 at 12:21 UTC

    Thanks a lot. I am still working to get a proper understanding but your proposal has already found a match in my example that I have overlooked!

Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: note [id://1042533]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others browsing the Monastery: (3)
As of 2025-06-23 03:58 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found

    Notices?
    erzuuliAnonymous Monks are no longer allowed to use Super Search, due to an excessive use of this resource by robots.