Day 21

[aoc2020.git] / 41.pl

diff --git a/41.pl b/41.pl
new file mode 100755 (executable)
index 0000000..846f78e
--- /dev/null
+++ b/41.pl
@@ -0,0 +1,46 @@
+#!/usr/bin/perl -w
+
+use strict;
+
+my %allergens;
+my %ingredients;
+my %in_count;
+
+while (<>) {
+       chomp;
+       my ($ingr, $al) = /\A([^\(]+) \(contains (.*)\)\z/;
+       my %ingr = map { $_ => 1 } split /\s+/, $ingr;
+       my @al = split /, /, $al;
+       for my $al (@al) {
+               if (defined $allergens{$al}) {
+                       for my $in1 (keys %{ $allergens{$al} }) {
+                               if (! $ingr{$in1}) {
+                                       delete $allergens{$al}->{$in1};
+                               }
+                       }
+               } else {
+                       $allergens{$al} = { %ingr };
+               }
+       }
+       for my $in (keys %ingr) {
+               $ingredients{$in} = {};
+               $in_count{$in}++;
+       }
+}
+
+for my $al (keys %allergens) {
+       for my $in (keys %{ $allergens{$al} }) {
+               print "$in can be $al.\n";
+               $ingredients{$in}->{$al} = 1;
+       }
+}
+
+my $sum = 0;
+for my $in (keys %ingredients) {
+       if (keys %{ $ingredients{$in} } == 0) {
+               # print "$in can't contain allergen\n";
+               $sum += $in_count{$in};
+       }
+}
+
+print "Sum=$sum\n";