Re: Matching permutations with regex

#!/usr/bin/perl -l

# https://en.wikipedia.org/wiki/Permutation#Generation_in_lexicographi
+c_order

use strict;
use warnings;

$_ = 'aabbcc';

1 while print,
  s/.*\K # find the last
  (.) # char such that
  (.*) # there is a later (latest)
  (.)(??{$1 ge $3 and '(*F)'}) # char greater than it
  (.*) # and get rest
  # swap those two chars ( $1 & $3 )
  # then reverse everything after the first swapped char
  / $3 . reverse $2.$1.$4 /xe
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Comment on Re: Matching permutations with regex Download Code

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Re^2: Matching permutations with regex by QM (Parson) on Nov 22, 2018 at 09:20 UTC
OK. That's probably pretty fast too. But I think you misunderstood? I can generate them, but I wanted to _match_ any permutation of a given string. Update: Oh, I had the `=~` backwards, and that led you astray. (Not shown in the OP is a programmatic way to generate the regex solution based on the input string, but that was left out for clarity.) -QM -- Quantum Mechanics: The dreams stuff is made of	[reply] [d/l]
Re^3: Matching permutations with regex by tybalt89 (Monsignor) on Nov 22, 2018 at 15:52 UTC
Like so ? `#!/usr/bin/perl -l # https://perlmonks.org/?node_id=1226058 use strict; use warnings; $_ = 'aabbcc'; my $len = length; my $inner = join ',', split //, tr///csr; my $glob = "{$inner}" x $len; my $re = "^(?=.{$len}\$)"; while( /./ ) { my $count = s/$&//g; $re .= "(?=(?:.*$&){$count})"; } $_ =~ $re and print for glob $glob;` [download] Outputs the 90 valid permutations.	[reply] [d/l]


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