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Perl: the Markov chain saw

Re: Efficient selection mechanism?

by ikegami (Pope)
on Jan 14, 2014 at 17:13 UTC ( #1070577=note: print w/replies, xml ) Need Help??

in reply to Efficient selection mechanism?

Not indexed, but a regex should search an 8k string pretty fast.
my $AoA = pack 'C*', map @$_, @AoA; my $omit = $AoA[0]; my $pat = '[^'.( join '', map quotemeta, pack 'C*', @$omit ).']{4}'; my $re = qr/\G(?:.{4})*?($pat)/s; my @matches = map [ unpack 'C*', $_ ], $AoA =~ /$re/g;

The following avoids recreating the original arrays at the expense of two bytes per element of @AoA.

my $AoA = pack '(C4S)*', map { @{ $AoA[$_] }, $_ } 0..$#AoA; my $omit = $AoA[0]; my $pat = '[^'.( join '', map quotemeta, pack 'C*', @$omit ).']{4}'; my $re = qr/\G(?:.{6})*?$pat(..)/s; my @matches = @AoA[ map unpack 'S', $AoA =~ /$re/g ];

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