Year 2018

[aoc.git] / 2018 / 16.pl

diff --git a/2018/16.pl b/2018/16.pl
new file mode 100755 (executable)
index 0000000..ab794e2
--- /dev/null
+++ b/2018/16.pl
@@ -0,0 +1,35 @@
+#!/usr/bin/perl -w
+
+use v5.30;
+use strict;
+
+my @tree = split /\s+/, <>;
+
+use List::Util qw(sum);
+
+sub walk {
+       my $subnodes = shift @tree;
+       my $metadata = shift @tree;
+       my $sum = 0;
+       say "walk $subnodes $metadata";
+       my $sn1 = $subnodes;
+       my @subvals;
+       while ($sn1--) {
+               push @subvals, walk();
+       }
+       if ($subnodes) {
+               while ($metadata--) {
+                       my $id = shift @tree;
+                       $id--;
+                       $sum += $subvals[$id]
+                               if $id < @subvals;
+               }
+       } else {
+               while ($metadata--) {
+                       $sum += shift @tree;
+               }
+       }
+       say "returning $sum";
+       $sum;
+}
+say walk();