Day 20: too many Homerbugs

diff --git a/2024/39.pl b/2024/39.pl
new file mode 100755 (executable)
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 (executable)
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;