Year 2018

[aoc.git] / 2018 / 21.pl

diff --git a/2018/21.pl b/2018/21.pl
new file mode 100755 (executable)
index 0000000..631f2f8
--- /dev/null
+++ b/2018/21.pl
@@ -0,0 +1,46 @@
+#!/usr/bin/perl -w
+
+use v5.30;
+use strict;
+
+my $serial = shift @ARGV;
+
+my %cache;
+sub power_at {
+       my ($x, $y) = @_;
+       return $cache{$x,$y} if defined $cache{$x,$y};
+
+       my $rack_id = $x + 10;
+       my $power = ($rack_id * $y + $serial) * $rack_id;
+       $power = "000" . $power;
+       $power =~ s/.*(.)..\z/$1/;
+       $power -= 5;
+       return $cache{$x,$y} = $power;
+}
+
+my ($maxx, $maxy, $maxpwr);
+for my $x (1 .. 300) {
+       for my $y (1 .. 300) {
+               my $sum;
+               for my $dx (0 .. 2) {
+                       next if $x + $dx > 300;
+                       for my $dy (0 .. 2) {
+                               next if $y + $dy > 300;
+                               $sum += power_at($x+$dx, $y+$dy);
+                       }
+               }
+               if (!defined $maxpwr || $sum > $maxpwr) {
+                       $maxpwr = $sum;
+                       $maxx = $x;
+                       $maxy = $y;
+               }
+       }
+}
+
+say power_at(33,45);
+say "$maxx,$maxy = $maxpwr";
+                       
+               
+       
+       
+