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Re: How can I improve this?

by lhoward (Vicar)
on Jul 25, 2000 at 21:34 UTC ( #24307=note: print w/replies, xml ) Need Help??

in reply to How can I improve this?

After a solid night's sleep I managed to come up with the following implementation that generates the permutations in the desired order without a separate sort step:
#!/usr/bin/perl -w use strict; # set up the initial 5 arrays into @a my @a=([0..2],[0..2],[0..2],[0..2],[0..2]); # build non-zero versions of those arrays my @nz=map {[grep {$_ != 0} @$_]} @a; # permute in order.... my @foo; foreach (15,14,13,11,7,12,10,6,9,5,3,8,4,2,1,0){ push @foo,@{permute('', ($_ & 0x01)?$nz[0]:[0], ($_ & 0x02)?$nz[1]:[0], $a[2], ($_ & 0x04)?$nz[3]:[0], ($_ & 0x08)?$nz[4]:[0]);} } # print out results print "$_\n" for (@foo); # permute lists recursively sub permute{ my ($prefix,$c,@arrays)=@_; my @ret=(); foreach(@$c){ my $f=$prefix.$_; if(scalar(@arrays)==0){ push @ret,$f; }else{ push @ret,@{permute($f,@arrays)}; } } return \@ret; }

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