use strict;
use Data::Dumper;
my $SIZE = shift || 4;
my @BOARD = map {[(1) x $SIZE]} (1..$SIZE);
my @SOLUTION;
my @TEMP;
scan(0,0,[@BOARD]);
print_solutions(\@SOLUTION);
#print Dumper \@SOLUTION;
sub scan {
#my ($col,$start_row,$board,$possible) = @_;
my ($col,$start_row,$board) = @_;
# no more columns?
if ($col == $SIZE) {
# found our solution!
push @SOLUTION,[@TEMP];
#print "found solution! (@TEMP)\n";
@TEMP = ();
return;
}
# find first available row
for my $row ($start_row..$SIZE-1) {
if($board->[$row]->[$col]) {
push @TEMP,$row;
#print "found available row: $row in col $col: (@TEMP)\n";
my $copy = [ map { [@$_] } @$board ];
mark_attacks($row,$col,$board);
#print_matrix($board);
scan($col+1,0,[@$board]);
$board = $copy;
}
}
pop @TEMP;
return;
}
sub mark_attacks {
my ($r,$c,$array) = @_;
$array->[$r]->[$c] = 'Q';
# mark horizontal
$array->[$r]->[$_] = 0 for ($c+1..$SIZE-1);
# mark r-c
$array->[--$r]->[++$c] = 0 while ($r > 0) && ($c < $SIZE-1);
# mark r+c
($r,$c) = @_;
$array->[++$r]->[++$c] = 0 while ($r < $SIZE-1) && ($c < $SIZE-1);
}
sub print_matrix { print join('',@$_),"\n" for @{+shift} }
sub print_solutions {
my @array = @{+shift};
for (@array) {
print join(' ',map { $_ + 1 } @$_),"\n";
}
print scalar @array, " solutions found\n";
}
####
$copy = [@$board];
##
##
$copy = [ map { [@$_] } @$board];