I came up with the below. Basically my intention was to avoid copying the arrays unless necessary. 

#!/usr/bin/perl
use strict;
use warnings;

my @list = (1 .. 5);
my $take = 2;

comb_demerphq(\@list, $take, []);

sub comb_demerphq {
    my ($items,$group,$list)=@_;
    return _comb_demerphq([ @{ $items||[] } ],$ group, [ @{ $list||[] 
+} ] );
}

sub _comb_demerphq {
    my ($items,$group,$list) = @_;

    unless ($group) {
        print "@$list\n";
    } else {
        my @newlist = (@$list,undef);
        while (@$items) {
                $newlist[-1]=shift (@$items);
                _comb_demerphq([@$items], $group - 1, \@newlist);
        }
    }
}

[download]

But i suspect that there are still better ways to improve this by using a different algorithm. Not sure what it is though.


---
demerphq

<Elian> And I do take a kind of perverse pleasure in having an OO assembly language...

In reply to Re: Printing combinations, code review request by demerphq
in thread Printing combinations, code review request by SparkeyG

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