From a4e1f82c3a7c63cf418e9ce63987b931792b7124 Mon Sep 17 00:00:00 2001
From: "Jan \"Yenya\" Kasprzak" <kas@fi.muni.cz>
Date: Thu, 14 Dec 2023 08:45:33 +0100
Subject: [PATCH] Day 14: more polished solution

---
 2023/27.pl | 23 +++++--------
 2023/28.pl | 95 +++++++++++++++---------------------------------------
 2 files changed, 34 insertions(+), 84 deletions(-)

diff --git a/2023/27.pl b/2023/27.pl
index ab6cbcd..d49d6b9 100755
--- a/2023/27.pl
+++ b/2023/27.pl
@@ -7,25 +7,18 @@ my $xmax = $#{ $map[0] };
 my $ymax = $#map;
 
 my $sum;
-my $retry = 1;
-while ($retry) {
-	$retry = 0;
-for my $y (1 .. $ymax) {
+for my $y (0 .. $ymax) {
 	for my $x (0 .. $xmax) {
-		if ($map[$y][$x] eq 'O' && $map[$y-1][$x] eq '.') {
-			$map[$y-1][$x] = 'O';
+		next if $map[$y][$x] ne 'O';
+		my $y1 = $y;
+		$y1-- while $y1 && $map[$y1-1][$x] eq '.';
+		if ($y1 != $y) {
+			$map[$y1][$x] = 'O';
 			$map[$y][$x] = '.';
-			$retry = 1;
 		}
+		$sum += $ymax + 1 - $y1;
 	}
 }
-}
-	
-say join('', @$_) for @map;
 
-for my $y (0 .. $ymax) {
-	for my $x (0 .. $xmax) {
-		$sum += $ymax + 1 - $y if $map[$y][$x] eq 'O';
-	}
-}
+say join('', @$_) for @map;
 say $sum;
diff --git a/2023/28.pl b/2023/28.pl
index 7135ca5..0699eb4 100755
--- a/2023/28.pl
+++ b/2023/28.pl
@@ -7,86 +7,43 @@ my $xmax = $#{ $map[0] };
 my $ymax = $#map;
 
 my %seen;
-my @rounds;
+my @score;
 my $round;
-while (1) {
-	$round++;
-	my $retry;
-	$retry = 1;
-	while ($retry) {
-		$retry = 0;
-		for my $y (1 .. $ymax) {
-			for my $x (0 .. $xmax) {
-				if ($map[$y][$x] eq 'O' && $map[$y-1][$x] eq '.') {
-					$map[$y-1][$x] = 'O';
-					$map[$y][$x] = '.';
-					$retry = 1;
-				}
-			}
-		}
-	}
-	$retry = 1;
-	while ($retry) {
-		$retry = 0;
-		for my $x (1 .. $xmax) {
-			for my $y (0 .. $ymax) {
-				if ($map[$y][$x] eq 'O' && $map[$y][$x-1] eq '.') {
-					$map[$y][$x-1] = 'O';
-					$map[$y][$x] = '.';
-					$retry = 1;
-				}
-			}
-		}
-	}
-	$retry = 1;
-	while ($retry) {
-		$retry = 0;
-		for my $y (reverse 0 .. $ymax-1) {
+my $key;
+
+while (++$round) {
+	for (1 .. 4) {
+		for my $y (0 .. $ymax) {
 			for my $x (0 .. $xmax) {
-				if ($map[$y][$x] eq 'O' && $map[$y+1][$x] eq '.') {
-					$map[$y+1][$x] = 'O';
-					$map[$y][$x] = '.';
-					$retry = 1;
-				}
-			}
-		}
-	}
-	$retry = 1;
-	while ($retry) {
-		$retry = 0;
-		for my $x (reverse 0 .. $xmax-1) {
-			for my $y (0 .. $ymax) {
-				if ($map[$y][$x] eq 'O' && $map[$y][$x+1] eq '.') {
-					$map[$y][$x+1] = 'O';
-					$map[$y][$x] = '.';
-					$retry = 1;
+				next if $map[$y][$x] ne 'O';
+				my $y1 = $y;
+				while ($y1 && $map[$y1-1][$x] eq '.') {
+					$map[$y1][$x] = '.';
+					$map[--$y1][$x] = 'O';
 				}
 			}
 		}
+
+		@map = map { # rotate clockwise
+			my $x = $_;
+			[ map { $map[$_][$x] } reverse 0 .. $ymax ]
+		} 0 .. $xmax;
+		($xmax, $ymax) = ($ymax, $xmax);
 	}
-		
-	# say join('', @$_) for @map;
 
-	my $sum;
+	$key = join("\n", map { join('', @$_) } @map);
+	last if $seen{$key};
+
+	my $sum = 0;
 	for my $y (0 .. $ymax) {
 		for my $x (0 .. $xmax) {
 			$sum += $ymax + 1 - $y if $map[$y][$x] eq 'O';
 		}
 	}
-	say $sum;
-	$rounds[$round] = $sum;
-	say "round $round sum $sum";
-	my $map = join("\n", map { join('', @$_) } @map);
-	if ($seen{$map}) {
-		say "round $round seen also at $seen{$map}";
-		my $period = $round - $seen{$map};
-		my $total = 1000000000;
-		$total -= $round;
-		$total %= $period;
-		say "looking at ", $round - $period + $total;
-		say $rounds[$round-$period+$total];
-		last;
-	}
-	$seen{$map} = $round;
+
+	$seen{$key} = $round;
+	$score[$round] = $sum;
 }
 
+my $remains = (1000000000 - $round) % ($round - $seen{$key});
+say $score[$seen{$key} + $remains];
-- 
2.43.5