First half of Year 2019

[aoc.git] / 2019 / 12.pl

diff --git a/2019/12.pl b/2019/12.pl
new file mode 100755 (executable)
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--- /dev/null
+++ b/2019/12.pl
@@ -0,0 +1,42 @@
+#!/usr/bin/perl -w
+
+use v5.16;
+use List::Util qw(sum);
+
+my %orb;
+while (<>) {
+       chomp;
+       my @b = split /\)/;
+       $orb{$b[0]}{$b[1]} = 1;
+}
+
+sub walk {
+       my ($b, $depth) = @_;
+       my @rv;
+       $rv[0] = 0 if $b eq 'YOU';
+       $rv[1] = 0 if $b eq 'SAN';
+       say "walking $b at $depth, rv=", ($rv[0] // '_'), ',', ($rv[1] // '_');
+       for my $x (keys %{ $orb{$b} }) {
+               say "$b->$x";
+               my ($v1, $v2) = walk($x, $depth+1);     
+               say "$b<-$x, rv=", ($rv[0] // '_'), ',', ($rv[1] // '_');
+               $rv[0] //= $v1;
+               $rv[1] //= $v2;
+               if (defined $rv[0] && defined $rv[1]) {
+                       say "Back at $b: $rv[0],$rv[1]";
+                       say $rv[0]+$rv[1] - 2;
+                       exit 0;
+               }
+       }
+       $rv[0]++ if defined $rv[0];
+       $rv[1]++ if defined $rv[1];
+       say "returning from $b at $depth, rv=", ($rv[0] // '_'), ',', ($rv[1] // '_');
+       return @rv;
+}
+
+walk('COM', 0);
+
+               
+               
+               
+