X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?p=aoc2020.git;a=blobdiff_plain;f=48.pl;fp=48.pl;h=f76f99355587fb9dde48d514f020d370eaf6eae1;hp=0000000000000000000000000000000000000000;hb=e3567af39d5b9459f3050d1c6b64ffc1f976b633;hpb=d26dd9c3d2edb1c6fecc3bf78c8cd0f1a1b9044f

diff --git a/48.pl b/48.pl
new file mode 100755
index 0000000..f76f993
--- /dev/null
+++ b/48.pl
@@ -0,0 +1,60 @@
+#!/usr/bin/perl -w
+
+use strict;
+
+my %tiles;
+
+my ($min_x, $max_x, $min_y, $max_y);
+
+while (<>) {
+	chomp;
+	my ($x, $y) = (0, 0);
+	while (length) {
+		s/\A(se|ne|sw|nw|e|w)//;
+		if ($1 eq 'ne') {
+			$y++;
+		} elsif ($1 eq 'e') {
+			$x++;
+		} elsif ($1 eq 'se') {
+			$x++; $y--;
+		} elsif ($1 eq 'sw') {
+			$y--;
+		} elsif ($1 eq 'w') {
+			$x--;
+		} elsif ($1 eq 'nw') {
+			$x--; $y++;
+		}
+	}
+	$tiles{"$x|$y"} ^= 1;
+	$min_x = $x if !defined $min_x || $min_x > $x;
+	$max_x = $x if !defined $max_x || $max_x < $x;
+	$min_y = $y if !defined $min_y || $min_y > $y;
+	$max_y = $y if !defined $max_y || $max_y < $y;
+}
+
+
+for (1 .. 100) {
+	$min_x--; $min_y--; $max_x++, $max_y++;
+	my %newtiles;
+	for my $x ($min_x .. $max_x) {
+	for my $y ($min_y .. $max_y) {
+		my $count = 0;
+		$count++ if $tiles{($x+1).'|'.($y)}; # E
+		$count++ if $tiles{($x).'|'.($y+1)}; # NE
+		$count++ if $tiles{($x+1).'|'.($y-1)}; # SE
+		$count++ if $tiles{($x).'|'.($y-1)}; # SW
+		$count++ if $tiles{($x-1).'|'.($y)}; # W
+		$count++ if $tiles{($x-1).'|'.($y+1)}; # NW
+		if ($tiles{"$x|$y"} && ($count == 0 || $count > 2)) {
+			$newtiles{"$x|$y"} = 0;
+		} elsif (!$tiles{"$x|$y"} && $count == 2) {
+			$newtiles{"$x|$y"} = 1;
+		} else {
+			$newtiles{"$x|$y"} = $tiles{"$x|$y"};
+		}
+	}
+	}
+	%tiles = %newtiles;
+	print "Tiles=" . (grep { $tiles{$_} } keys %tiles)."\n";
+}
+