in reply to Challenge: Generate fixed size combination across groups without duplicates

A sample to work with:

group_1 = A B C
group_2 = 1 2 3 4
group_3 = yellow blue green
group_4 = tiny small medium large gigantic

fixed_size = 2

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Can't you just use standard techniques to pick all combinations of 2 out of a set of 4, picking pairs of groups, then for each pair, calculate the Cartesian product?
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Re^2: Challenge: Generate fixed size combination across groups without duplicates
by Limbic~Region (Chancellor) on Nov 16, 2011 at 14:38 UTC
    JavaFan,
    Well, that only works for the sample provided and not the larger problem of a variable number of groups but it is trivial to extend it to the general case. I simply need to reverse the solution I provided in the original problem description:
    • Use any fixed size combination iterator to produce the combination of groups matching the fixed size target
    • Use Algorithm::Loops or similar to generate the cartesian product

    This is also much simpler than the odometer model solution I came up with last night after posting this. Thanks.

    Cheers - L~R

[reply]
      I arrived at the same solution:
      use Algorithm::Loops;
use Math::Combinatorics;

my $fixed_size = 2;
my @groups = (
    [qw( A B C )],
    [qw( 1 2 3 4 )],
    [qw( yellow blue green )],
    [qw( tiny small medium large gigantic )],
);

for my $fixed_size_groups ( combine( $fixed_size, @groups ) ) {
    Algorithm::Loops::NestedLoops $fixed_size_groups, sub {
        print "@_\n";
    };
}

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        I got the same. ++
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        I used you code for my own problem and it worked fine in the beginning but the moment I add another array to @groups the order of the arrays changes intern.I have little experiences with subs so I don't know how to change the code to make sure the order stays the same?

        my @groups=(
[qw( yes no 0 )],
[qw( yes all 0 )],
[qw( all stop 0 )],
[qw( 1 0 )],
[qw( 1 0 )],    );        
my @names=('rscode','nonsyn','aac','splice','var');
my $fixed_size=scalar(@names);    
my ($combo,$count)= create_combo($fixed_size,\@groups);    

sub create_combo 
{
    my @array;
    my $count=0;
    my $fixed_size= $_[0];
    my $groups=$_[1];
    for my $fixed_size_groups ( combine( $fixed_size, @{$groups} ) ) 
    {    Algorithm::Loops::NestedLoops $fixed_size_groups, 
        sub {
            push @array,@_;    
            print "@_\n";
            $count++;
           };
  return (\@array,$count);
  }

    
}

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        It gives as result 

        1 all 1 yes yes
1 all 1 yes all
1 all 1 yes 0
....

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        which are the right combinations but not the right order of the elements! Any help is much appreciated.

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