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lib/Games/Sudoku/General.pm  view on Meta::CPAN

my %constraint_method = (
    '?' => '_constraint_backtrack',
);

sub _constrain {
    my ( $self ) = @_;
    my $stack = $self->{backtrack_stack} ||= [];	# May hit this
							# when initializing.
    my $used = $self->{constraints_used} ||= {};
    my $iterations;
    $iterations = $self->{iteration_limit}
	if $self->{iteration_limit} > 0;

    $self->{no_more_solutions} and
	return $self->_unload (undef, SUDOKU_NO_SOLUTION);

    @{$self->{backtrack_stack}} and do {
	$self->_constraint_remove and
	    return $self->_unload (undef, SUDOKU_NO_SOLUTION);
    };

lib/Games/Sudoku/General.pm  view on Meta::CPAN

	}	# Next set containing vacant cells
    }	# Next order

    return [];
}

# ? constraint - initiate backtracking.

sub _constraint_backtrack {
    my ( $self ) = @_;
##  --$iterations >= 0 or return $self->_unload ('', SUDOKU_TOO_HARD)
##	if defined $iterations;
    my @try;
    my $syms = @{$self->{symbol_list}};
    foreach my $cell (@{$self->{cell}}) {
	next if $cell->{content};
	next unless @{$cell->{membership}};
	my $possible = 0;
	for (my $val = 1; $val < $syms; $val++) {
	    $possible++ unless $cell->{possible}{$val};
	}
	$possible or return ['backtrack'];