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interesting approach that reminded me about some old project that needed some permutations generations stuff... so, i've checked up that code and here i come with a reviewed standalone version:
#!/usr/bin/perl -w # DESCRIPTION: Generate permutations in lexicographic order # USAGE: ./ <term1> <term2> <term3> ..... use strict; die "bleah... nothing to permutate\n" if $#ARGV<0; my @terms = @ARGV; my $n = $#ARGV; my @a = (0..$n); genperm(); exit(0); sub genperm { print join(" ",@terms[@a]),"\n"; my ($k,$j) = ($n-1,$n); $k-- while ($k>=0 and $a[$k]>$a[$k+1]); return(0) if ($k<0); $j-- while ($a[$k]>$a[$j]); swap($j,$k++); $j=$n; swap($j--,$k++) while ($j>$k); genperm(); } sub swap { my ($i,$j) = @_; my $t = $a[$i]; ($a[$i],$a[$j]) = ($a[$j],$t); }

as you may see, it's a pure lexicographic permutations generator algorithm, as in the books ;-)

oh, not to forget, just checked up on cpan and found out there is a Algorithm::Permute module. here is a lame example for module users ;-)

#!/usr/bin/perl -w use strict; die "bleah... nothing to permutate\n" unless defined @ARGV; use Algorithm::Permute qw(permute permute_ref); print join(" ", @$_), "\n" for permute(\@ARGV);


In reply to RE: Permutations and combinations by AltBlue
in thread Permutations and combinations by merlyn

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