X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?p=aoc2020.git;a=blobdiff_plain;f=39.pl;h=40f98aba42571768747e64f5b655efb383fdacf3;hp=2b88a89ba862f94b3b7d1267bd36299596503aa5;hb=HEAD;hpb=3dcbc8cbbed0a020192974ba29b73f0164b49ce2

diff --git a/39.pl b/39.pl
index 2b88a89..40f98ab 100755
--- a/39.pl
+++ b/39.pl
@@ -2,74 +2,56 @@
 
 use strict;
 
-local $/ = "\n\n";
+sub rows2str {
+	my (@rows) = @_;
+	return join("\n", @rows) . "\n";
+}
+
+sub rotate {
+	my ($str) = (@_);
+	my $dim =()= $str =~ /(\n)/g;
+	my $newstr = '';
+	for my $y (0 .. $dim-1) {
+		for my $x (0 .. $dim-1) {
+			$newstr .= substr($str, $y + ($dim+1)*($dim - $x - 1), 1);
+		}
+		$newstr .= "\n";
+	}
+	return $newstr;
+}
+
+sub flip {
+	my ($str) = @_;
+	return rows2str(map { join('', reverse split //) } split /\n/, $str);
+}
 
-sub invbits {
-	my ($in) = @_;
-	return (($in & 1) << 9)
-		| (($in & 2) << 7)
-		| (($in & 4) << 5)
-		| (($in & 8) << 3)
-		| (($in & 16) << 1)
-		| (($in & 32) >> 1)
-		| (($in & 64) >> 3)
-		| (($in & 128) >> 5)
-		| (($in & 256) >> 7)
-		| (($in & 512) >> 9);
+sub rotate_or_flip {
+	my ($str, $count) = @_;
+	return $count == 4 ? flip($str) : rotate($str);
 }
 
-my %tiles;
-my %sides;
-my %side2tiles;
+sub top_side {
+	$_[0] =~ /\A(.*?)\n/xms;
+	return $1;
+}
+
+my %top2tile;
+
+local $/ = "\n\n";
+
 while (<>) {
-	my ($id, @rows) = split /\n/;
-	$id =~ s/Tile //;
-	$id =~ s/://;
-	@rows = map { y/#./10/; oct "0b$_" } @rows;
-	$tiles{$id} = \@rows;
-	$sides{$id} = [
-		$rows[0],
-		(($rows[0] & 1) << 9)
-		| (($rows[1] & 1) << 8)
-		| (($rows[2] & 1) << 7)
-		| (($rows[3] & 1) << 6)
-		| (($rows[4] & 1) << 5)
-		| (($rows[5] & 1) << 4)
-		| (($rows[6] & 1) << 3)
-		| (($rows[7] & 1) << 2)
-		| (($rows[8] & 1) << 1)
-		| (($rows[9] & 1) << 0),
-		$rows[9],
-		(($rows[0] & 512) >> 0)
-		| (($rows[1] & 512) >> 1)
-		| (($rows[2] & 512) >> 2)
-		| (($rows[3] & 512) >> 3)
-		| (($rows[4] & 512) >> 4)
-		| (($rows[5] & 512) >> 5)
-		| (($rows[6] & 512) >> 6)
-		| (($rows[7] & 512) >> 7)
-		| (($rows[8] & 512) >> 8)
-		| (($rows[9] & 512) >> 9),
-	];
-	print "Tile <$id> sides ", join(',', @{ $sides{$id} }), "\n";
-	for my $side (@{ $sides{$id} }) {
-		push @{ $side2tiles{$side} }, $id;
-		push @{ $side2tiles{invbits($side)} }, $id;
+	my ($id, $data) = /\ATile\s+(\d+):\n(.*?\n)\n?\z/xms;
+	for (1 .. 8) {
+		push @{ $top2tile{top_side($data)} }, $id;
+		$data = rotate_or_flip($data, $_);
 	}
 }
 
 my %single_ids;
-for my $side (keys %side2tiles) {
-	print "side $side: ", join(',', @{ $side2tiles{$side} }), "\n";
-	# print "inv  ", invbits($side), "\n";
-	if (scalar @{ $side2tiles{$side} } == 1
-		&& scalar @{ $side2tiles{invbits($side)} } == 1) {
-		print "side $side of tile $side2tiles{$side}->[0] is single\n";
-		$single_ids{$side2tiles{$side}->[0]}++;
-	}
-	
+for my $row (keys %top2tile) {
+	next if @{ $top2tile{$row} } != 1;
+	$single_ids{ $top2tile{$row}->[0] }++;
 }
 
 my @corners = grep { $single_ids{$_} == 4 } keys %single_ids;
-print join('*', @corners), '=', eval join('*', @corners), "\n"
-
+print join('*', @corners), '=', eval join('*', @corners), "\n";