generic solution for arbitrary number of ordered sets to be combined

use v5.10.0;
use warnings;
use strict;
use Data::Dump qw/pp/;

my @sets = ( ["A".."C"], [("-") x 3] );

my (@path,@results);

sub branch {
  my $done=1;
 
  for my $set ( @sets ){
    if (@$set ) {
      $done=0;
      push @path, shift @$set;       
      branch();
      unshift @$set, pop @path;
    }
  }
  
  if ($done){
    push @results, join "",@path;
  }

}

branch();

pp \@results;

__END__
[
  "ABC---",
  "AB-C--",
  "AB--C-",
  "AB---C",
  "A-BC--",
  "A-B-C-",
  "A-B--C",
  "A--BC-",
  "A--B-C",
  "A---BC",
  "-ABC--",
  "-AB-C-",
  "-AB--C",
  "-A-BC-",
  "-A-B-C",
  "-A--BC",
  "--ABC-",
  "--AB-C",
  "--A-BC",
  "---ABC",
]

[download]

Cheers Rolf

( addicted to the Perl Programming Language)

update

simplified code

update

Formula: be s_1,s_2,...s_n the size of n sets in @sets, the number of combinations is then

 fac( sum( s_i)  )
-------------------
 prod ( fac (s_i) )

[download]

or

( Σ si ) ! 
---------- 
  Π (si!)

In reply to Re: combinations of given string by LanX
in thread combinations of given string by Anonymous Monk

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