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use strict;
use warnings;

my $NUM_RULES = 8;
my $NUM_LINES = 15;
my %rule_table = ();

sub log2($)
{
    return log($_[0]) / log(2);
}

sub int2bitvec($$)
{
    my ($l, $n) = @_;
    my @s = ();
    unshift @s, ($n >> $l) & 1 while $l--;
    return @s;
}

sub bitvec2str($)
{
    return join '', reverse @{$_[0]};
}

sub build_rules($)
{
    my @v = int2bitvec($NUM_RULES, $_[0]);

    for (my $i = 0; $i < $NUM_RULES; ++$i)
    {
        my @t = int2bitvec(log2($NUM_RULES), $i);
        $rule_table{bitvec2str(\@t)} = $v[$i];
    }
}

sub print_rules()
{
    print "\n";
    foreach my $key (sort keys %rule_table)
    {
        print "$key = $rule_table{$key}\n";
    }
}

sub line_length($)
{
    return 2 * $_[0] + 1;
}

print "Enter a rule: ";
my $n = <STDIN>;

($n =~ /^\d+$/ and $n < 2 ** $NUM_RULES)
    or die "Please specify a positive integer less than " .(2 ** $NUM_RULES). "\n";

build_rules($n);
#print_rules();
print "\n";

my $prev_line = "";
my $curr_line = "1";
my $pad_print = "";
my $line_print = "";
my $pad = "";

for (my $i = 0; $i < $NUM_LINES; ++$i)
{
    $prev_line = $curr_line;
    $curr_line = "";
    $pad = 0 x (((line_length($NUM_LINES) + 2) - line_length($i)) / 2);

    $pad_print = $pad;
    $pad_print =~ s/0/ /g;

    $line_print = $prev_line;
    $line_print =~ s/0/ /g;
    $line_print =~ s/1/x/g;

    print $pad_print . $line_print . $pad_print . "\n";

    for (my ($c, $j) = (0, (line_length($NUM_LINES) - line_length($i)) / 2 - 1);
        $c < line_length($i + 1); ++$c, ++$j)
    {
        $curr_line .= $rule_table{substr($pad . $prev_line . $pad, $j, 3)};
    }
}