From 1853ec1de5d2f229724bc24c1c9b3d3c1572affc Mon Sep 17 00:00:00 2001
From: "Jan \"Yenya\" Kasprzak" <kas@fi.muni.cz>
Date: Mon, 13 Dec 2021 06:28:05 +0100
Subject: [PATCH] Day 13: more off-by-one errors.

---
 25.pl | 38 ++++++++++++++++++++++++++++++++++++++
 26.pl | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100755 25.pl
 create mode 100755 26.pl

diff --git a/25.pl b/25.pl
new file mode 100755
index 0000000..ceeb16f
--- /dev/null
+++ b/25.pl
@@ -0,0 +1,38 @@
+#!/usr/bin/perl -w
+
+use v5.16;
+
+my %dots;
+
+while (<>) {
+	chomp;
+	my ($x, $y) = split /,/;
+	last if !defined $y;
+	$dots{$x}{$y}++;
+}
+
+my ($maxx, $maxy);
+while (<>) {
+	chomp;
+	my ($axis, $val) = /fold along (.)=(\d+)/;
+
+	for my $x (keys %dots) {
+	for my $y (keys %{$dots{$x}}) {
+		if ($axis eq 'x' && $x > $val) {
+			$dots{2*$val - $x}{$y}++;
+			delete $dots{$x}{$y};
+		} elsif ($axis eq 'y' && $y > $val) {
+			$dots{$x}{2*$val - $y}++;
+			delete $dots{$x}{$y};
+		}
+	} }
+	last;
+}
+
+my $sum;
+for my $x (keys %dots) {
+	$sum += keys %{$dots{$x}};
+}
+
+say $sum;
+
diff --git a/26.pl b/26.pl
new file mode 100755
index 0000000..c789704
--- /dev/null
+++ b/26.pl
@@ -0,0 +1,40 @@
+#!/usr/bin/perl -w
+
+use v5.16;
+
+my %dots;
+
+while (<>) {
+	chomp;
+	my ($x, $y) = split /,/;
+	last if !defined $y;
+	$dots{$x}{$y}++;
+}
+
+my ($maxx, $maxy);
+while (<>) {
+	chomp;
+	my ($axis, $val) = /fold along (.)=(\d+)/;
+
+	$maxx = $val if $axis eq 'x' && (!$maxx || $maxx > $val);
+	$maxy = $val if $axis eq 'y' && (!$maxy || $maxy > $val);
+
+	for my $x (keys %dots) {
+	for my $y (keys %{$dots{$x}}) {
+		if ($axis eq 'x' && $x > $val) {
+			$dots{2*$val - $x}{$y}++;
+			delete $dots{$x}{$y};
+		} elsif ($axis eq 'y' && $y > $val) {
+			$dots{$x}{2*$val - $y}++;
+			delete $dots{$x}{$y};
+		}
+	} }
+}
+
+for my $y (0 .. $maxy) {
+	for my $x (0 .. 40) {
+		print $dots{$x}{$y} ? '#' : ' ';
+	}
+	print "\n";
+}
+
-- 
2.43.0