From: Jan "Yenya" Kasprzak <kas@fi.muni.cz>
Date: Fri, 20 Dec 2024 05:55:31 +0000 (+0100)
Subject: Day 20: too many Homerbugs
X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?a=commitdiff_plain;h=9e6c55c4bc23935a406791d2461b72a6931e72fa;p=aoc.git

Day 20: too many Homerbugs
---

diff --git a/2024/39.pl b/2024/39.pl
new file mode 100755
index 0000000..474143a
--- /dev/null
+++ b/2024/39.pl
@@ -0,0 +1,49 @@
+#!/usr/bin/perl -w
+
+use v5.40;
+
+my @map;
+my ($x, $y);
+while (<>) {
+	chomp;
+	if (/S/g) {
+		$x = pos()-1;
+		$y = $.-1;
+	}
+	push @map, [ split // ];
+}
+my $xmax = $#{$map[0]};
+my $ymax = $#map;
+
+sub walk {
+	my ($x, $y) = @_;
+
+	my @q = [0, $x, $y];
+	my %seen;
+	while (@q) {
+		my ($cost, $x, $y) = @{ shift @q };
+		next if $seen{"$x,$y"}++;
+		if ($map[$y][$x] eq 'E') {
+			return $cost;
+		}
+		for my ($dx, $dy) (-1, 0, 1, 0, 0, -1, 0, 1) {
+			my ($nx, $ny) = ($x+$dx, $y+$dy);
+			next if $map[$ny][$nx] eq '#';
+			push @q, [$cost+1, $nx, $ny];
+		}
+	}
+	return undef;
+}
+
+my $base = walk($x, $y);
+my $count = 0;
+for my $y1 (1 .. $#map -1) {
+	for my $x1 (1 .. $#{ $map[0] } -1) {
+		next if $map[$y1][$x1] ne '#';
+		$map[$y1][$x1] = '.';
+		my $s = walk($x, $y);
+		$count++ if $base - $s >= 100;
+		$map[$y1][$x1] = '#';
+	}
+}
+say $count;
diff --git a/2024/40.pl b/2024/40.pl
new file mode 100755
index 0000000..1f7dafb
--- /dev/null
+++ b/2024/40.pl
@@ -0,0 +1,54 @@
+#!/usr/bin/perl -w
+
+use v5.40;
+
+my @map;
+my ($x, $y);
+while (<>) {
+	chomp;
+	if (/E/g) {
+		$x = pos()-1;
+		$y = $.-1;
+	}
+	
+	push @map, [ split // ];
+}
+my $xmax = $#{ $map[0] };
+my $ymax = $#map;
+
+my %dist;
+my @q = [0, $x, $y];
+while (@q) {
+	my ($cost, $x, $y) = @{ shift @q };
+	next if defined $dist{"$x,$y"};
+	$dist{"$x,$y"} = $cost;
+	for my ($dx, $dy) (-1, 0, 1, 0, 0, -1, 0, 1) {
+		my ($nx, $ny) = ($x+$dx, $y+$dy);
+		next if $map[$ny][$nx] eq '#';
+		push @q, [$cost+1, $nx, $ny];
+	}
+}
+
+my $base = $dist{"$x,$y"};
+my $count = 0;
+my $lim = 20;
+my $min = 100;
+for my $y1 (1 .. $ymax -1) {
+	for my $x1 (1 .. $xmax-1) {
+		next if !exists $dist{"$x1,$y1"};
+		for my $dx (-$lim .. $lim) {
+			for my $dy (-$lim+abs($dx) .. $lim-abs($dx)) {
+				my ($nx, $ny) = ($x1+$dx, $y1+$dy);
+				next if $nx < 0 || $nx > $xmax
+					|| $ny < 0 || $ny > $ymax
+					|| $map[$ny][$nx] eq '#'
+					|| !exists $dist{"$nx,$ny"};
+				my $saved =
+					+ $dist{"$x1,$y1"} - $dist{"$nx,$ny"}
+					- (abs($dx)+abs($dy));
+				$count++ if $saved >= $min;
+			}
+		}
+	}
+}
+say $count;