From: Jan "Yenya" Kasprzak <kas@fi.muni.cz>
Date: Fri, 8 Dec 2023 07:54:41 +0000 (+0100)
Subject: Day 8: more polished but still incorrect solution
X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?p=aoc.git;a=commitdiff_plain;h=93aa51b44022ee9169d7fc519d458a164572dfe9

Day 8: more polished but still incorrect solution
---

diff --git a/2023/15.pl b/2023/15.pl
index e003111..83ad39f 100755
--- a/2023/15.pl
+++ b/2023/15.pl
@@ -2,27 +2,21 @@
 
 use v5.38;
 
-$/ = "\n\n";
+chomp(my $steps = <>);
+my @steps = split //, $steps;
+
+scalar <>;
+
 my %dirs;
-my @steps = split //, scalar <>;
-pop @steps;
-pop @steps;
-my $l = <>;
-for (split /\n/, $l) {
-	my @x = /[A-Z]{3}/g;
+while (<>) {
+	my @x = /\w{3}/g;
 	$dirs{$x[0].'L'} = $x[1];
 	$dirs{$x[0].'R'} = $x[2];
 }
 
-my %seen;
-my $now = 'AAA' . $steps[0];
+my $now = 'AAA';
 my $i = 0;
-my $n;
-while ($now !~ /^ZZZ/) {
-	say $now;
-	$i ++;
-	$i = 0 if $i >= @steps;
-	$now = $dirs{$now}.$steps[$i];
-	$n++;
+while ($now ne 'ZZZ') {
+	$now = $dirs{$now . ($steps[$i++ % @steps])};
 }
-say $n;
+say $i;
diff --git a/2023/16.pl b/2023/16.pl
index 5e7f823..d2b6944 100755
--- a/2023/16.pl
+++ b/2023/16.pl
@@ -1,45 +1,47 @@
 #!/usr/bin/perl -w
 
 use v5.38;
+use List::Util 'uniq';
+
+chomp(my $steps = <>);
+my @steps = split //, $steps;
+
+scalar <>;
 
-$/ = "\n\n";
 my %dirs;
-my @steps = split //, scalar <>;
-pop @steps;
-pop @steps;
-my $l = <>;
-for (split /\n/, $l) {
-	my @x = /[A-Z0-9]{3}/g;
+while (<>) {
+	my @x = /\w{3}/g;
 	$dirs{$x[0].'L'} = $x[1];
 	$dirs{$x[0].'R'} = $x[2];
 }
 
-my %seen;
-my %now = map { substr($_, 0, 3) . $steps[0] => 1 } grep { /^..A/ } keys %dirs;
-my @now = keys %now;
-say join(' ', @now);
-
 sub walk {
-	my $node = shift;
+	my $now = shift;
 	my $i = 0;
-	my $n;
-	while ($node !~ /^..Z/) {
-		$i++;
-		$i = 0 if $i >= @steps;
-		$node = $dirs{$node} . $steps[$i];
-	$n++;
+	while ($now !~ /Z$/) {
+		$now = $dirs{$now . ($steps[$i++ % @steps])};
+	}
+	return $i;
+}
+
+sub gcd {
+	my ($x, $y) = @_;
+	($x, $y) = ($y, $x) if $y > $x;
+	while ($y) {
+		($x, $y) = ($y, $x % $y);
 	}
-	return $n;
+	return $x;
 }
 
-my %f;
-use List::Util qw(product);
-for (@now) {
-	my $st = walk($_);
-	my $l = `factor $st`;
-	$l =~ s/.*://;
-	for my $n ($l =~ /\d+/g) {
-		$f{$n}++;
+# using LCM is incorrect in general case,
+# but it works on the actual puzzle input
+my $p;
+for (uniq grep { /A$/ } map { substr($_, 0, 3) } keys %dirs) {
+	my $steps = walk($_);
+	if (defined $p) {
+		$p *= $steps/gcd($p, $steps);
+	} else {
+		$p = $steps;
 	}
 }
-say product keys %f;
+say $p;