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# more update: this is the tested version now!! sub CountSubstrings { # $string1, $string2, $substr_length my $l = pop @_; my %found = (); my %match = (); my $first = 2; my $string1 = $_[0]; for my $string ( @_ ) { $first --; my $ls = length( $string ); my $limit = $ls - $l + 1; for ( my $i = 0; $i < $limit; $i++ ) { my $sbstr = substr( $string, $i, $l ); $first or defined ( $match{$sbstr} ) && next(); $found{ $sbstr }{ $string } ||= 1; $first and next;; defined ( $found{ $sbstr }{ $string1 } ) and $match{ $sbstr } = 1; } } Count( keys %match ); } sub Count { 1+$#_ };
Description of alggorithm: Store all substrings of string 1 of the given length in subhash $found{ $string1 }; do the same for string 2 but in addition lookup in the first hash and record any matches in the %match hash. The suggested opportunities for optimisation include (a) only need to check matches for the substring iteration of the second string. (b) only need to build the substring for string 2 if there is no match found in the match hash.


Free your mind

In reply to Re: Challenge: Fast Common Substrings by Moron
in thread Challenge: Fast Common Substrings by Limbic~Region

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    [Corion]: LanX: Ah, yeah - Frankfurt is in the quake region, but at the very border. I think I've never noticed a quake in Frankfurt myself
    [marto]: good morning all
    [Corion]: On another topic, in the process of Rubber Duck SoPWing, I wrote a post about the best API for generating HTTP requests (not sending them) and while writing it and fleshing out my sample implementation, I came up with some improvements to my ...
    [Corion]: ... existing prototype. Cartesian Products will be proud of that module once it gets out ;)
    [Corion]: Hi marto ;)

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