#!/usr/bin/perl -w
use strict;
# -----------------------------------------------
# Here's some golf-ish code that loops through the
# given combinations, as well as a clearer rendition.
# It uses a hash to eliminate duplicates, and
# strings rather than an array for each combo.
# I expect it can be done in many fewer strokes,
# but I had fun playing around with it, anyway,
# and this four liner looked obfuscated enough.
# The output is listed at the end.
my($N,$M)=(8,6);my%c;r($N,join('',1..$N));sub
r{my($n,$s)=@_;if($n==$M){$c{$s}++unless$c{$s};}else
{for(1..$N){$t=~s/$_/#/,r($n-1,$t)if(our$t=$s)=~/$_/;}}}
print join($/,sort keys %c),"$/Total=",scalar(keys %c),$/;
_END__
# A clearer version of the same thing.
my ($N,$M) = (8,6);
my %combos = ();
recursive($N,join('',1..$N));
sub recursive {
my ($n,$combo) = @_;
if ($n==$M){
$combos{$combo}++ unless $combos{$combo};
}
else {
for my $i (1..$N){
if ( (my $tmp=$combo) =~ /$i/ ){
$tmp=~s/$i/#/;
recursive($n-1,$tmp);
}
}
}
}
print
"-- Combinations of $N things with ",
$N-$M, " crossed out. --\n",
join("\n", sort keys %combos),
"\n-- Total number is ", scalar(keys %combos),
". --\n\n";
# -------- output of the short one -------------
##345678
#2#45678
#23#5678
#234#678
#2345#78
#23456#8
#234567#
1##45678
1#3#5678
1#34#678
1#345#78
1#3456#8
1#34567#
12##5678
12#4#678
12#45#78
12#456#8
12#4567#
123##678
123#5#78
123#56#8
123#567#
1234##78
1234#6#8
1234#67#
12345##8
12345#7#
123456##
Total=28
