Year 2018

[aoc.git] / 2018 / 14.pl

diff --git a/2018/14.pl b/2018/14.pl
new file mode 100755 (executable)
index 0000000..41f45db
--- /dev/null
+++ b/2018/14.pl
@@ -0,0 +1,29 @@
+#!/usr/bin/perl -w
+
+use v5.30;
+use strict;
+
+my %prereqs;
+my %steps;
+while (<>) {
+       my ($src, $dst) = /(\w) must be.* (\w) can/;
+       $prereqs{$dst}->{$src} = 1;
+       $steps{$src} = ord($src)-ord('A')+61;
+       $steps{$dst} = ord($dst)-ord('A')+61;
+}
+
+my $time = 0;
+while (%steps) {
+       $time++;
+       my @avail = sort grep { keys %{ $prereqs{$_} } == 0 } keys %steps;
+       for my $step (splice @avail, 0, 5) {
+               next if --$steps{$step} > 0;
+               delete $steps{$step};
+               for my $p (keys %prereqs) {
+                       delete $prereqs{$p}->{$step};
+               }
+       }
+}
+
+say $time;
+