in reply to Re: How can I improve this?
in thread How can I improve this?

Since you seemed interested.. here is my permutation generator. It takes a base string (should be empty) as its first argument, then refrences to as many lists as you want as the other arguments and returns a refrence to a list containg all the list-element concatination permutations: 
my $foo=permute('',[0..2],[0..2],[0..3],[0..2]);

sub permute{
  my $prefix=shift;
  my @arrays=@_;
  my $c=shift @arrays;
  my @ret=();
  foreach(@$c){
    my $f=$prefix.$_;
    if(scalar(@arrays)==0){
      push @ret,$f;
    }else{
      my $t=permute($f,@arrays);
      push @ret,@$t;
    }
  }
  return \@ret;
}

[download]
I'm not really happy with the implementation of it, but I like it in spirit (of course, I'm a big fan of recursive algorithms to begin with).

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My permutor
by merlyn (Sage) on Jul 25, 2000 at 07:57 UTC
    Well, since everyone is posting their permutors, here's mine: 
    sub permute {
  my $last = pop @_;
  unless (@_) {
    return @$last;
  }
  return map { my $left = $_; map "$left$_", @$last } permute(@_);
}

    [download]

    -- Randal L. Schwartz, Perl hacker

[reply]
[d/l]
      Drool....

      Oh I like that.

      Mmmm,
      Gryn

[reply]

      does this work? how do you call it?

[reply]

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