day9.pl

use 5.018;

my %nodes = ();

open(my $fh, '<', 'input') or die "can't read input: $!";

while (my $line = <$fh>) {
	if ($line =~ /^(\w+) to (\w+) = (\d+)$/) {
		$nodes{$1}{$2} = $3;
		$nodes{$2}{$1} = $3;
	}
}

close($fh);

my @distances = ();

sub chart_from {
	my ($start, $dist, $remaining) = @_;
	my @remaining = @$remaining;

	if (@remaining == 0) {
		say "done: $dist";
	}

	foreach my $next (@remaining) {
		my @thisremaining = grep { $_ ne $next } @remaining;
		chart_from($next, $dist + $nodes{$start}{$next}, \@thisremaining);
	}
}

foreach my $start (keys %nodes) {
	my @remaining = grep { $_ ne $start } keys %nodes;
	chart_from($start, 0, \@remaining);
}