From 48892957f640e94a6940a0332fb1da6af117762d Mon Sep 17 00:00:00 2001
From: "Jan \"Yenya\" Kasprzak" <kas@fi.muni.cz>
Date: Sat, 25 Dec 2021 06:19:27 +0100
Subject: [PATCH] Day 25: pretty straightforward

---
 49.pl | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100755 49.pl

diff --git a/49.pl b/49.pl
new file mode 100755
index 0000000..831140f
--- /dev/null
+++ b/49.pl
@@ -0,0 +1,70 @@
+#!/usr/bin/perl -w
+
+use v5.16;
+
+my @m = map { chomp; [ split // ] } <>;
+
+my $xmax = @{ $m[0] };
+my $ymax = @m;
+
+sub print_map {
+	my $m = shift;
+	for my $row (@m) {
+		say join('', @$row);
+	}
+	say "";
+}
+
+my $step;
+my $moved;
+do {
+	$moved = 0;
+	my @m1;
+	for my $y (0 .. $ymax-1) {
+		for my $x (0 .. $xmax-1) {
+			if ($m[$y][$x] eq '>') {
+				my $nx = $x+1;
+				$nx = 0 if $nx >= $xmax;
+				if ($m[$y][$nx] eq '.') {
+					$m1[$y][$nx] = '>';
+					$m1[$y][$x] = '.';
+					$moved++;
+				} else {
+					$m1[$y][$x] = $m[$y][$x];
+				}
+			} else {
+				if (!defined $m1[$y][$x]) {
+					$m1[$y][$x] = $m[$y][$x];
+				}
+			}
+		}
+	}
+	@m = @m1;
+	@m1 = ();
+
+	for my $y (0 .. $ymax-1) {
+		for my $x (0 .. $xmax-1) {
+			if ($m[$y][$x] eq 'v') {
+				my $ny = $y+1;
+				$ny = 0 if $ny >= $ymax;
+				if ($m[$ny][$x] eq '.') {
+					$m1[$ny][$x] = 'v';
+					$m1[$y][$x] = '.';
+					$moved++;
+				} else {
+					$m1[$y][$x] = $m[$y][$x];
+				}
+			} else {
+				if (!defined $m1[$y][$x]) {
+					$m1[$y][$x] = $m[$y][$x];
+				}
+			}
+		}
+	}
+	@m = @m1;
+	$step++;
+	print_map(\@m);
+} while ($moved);
+
+say "$step steps";
+
-- 
2.43.5