The rest of Year 2017

[aoc.git] / 2017 / 37.pl

diff --git a/2017/37.pl b/2017/37.pl
new file mode 100755 (executable)
index 0000000..6a21e09
--- /dev/null
+++ b/2017/37.pl
@@ -0,0 +1,48 @@
+#!/usr/bin/perl
+
+use v5.30;
+use strict;
+
+my @map = map { chomp; [ split // ] } <>;
+
+my $xmax = @{ $map[0] };
+my $ymax = @map;
+
+my $x;
+for (0 .. $xmax) {
+       if ($map[0][$_] eq '|') {
+               $x = $_;
+               last;
+       }
+}
+my $y = 0;
+my $dir = 2; # 0 up, 1 right, 2 down, 3 left
+
+my $seen = '';
+while (1) {
+       my $now = $map[$y][$x];
+       say "at $x,$y: '$now'";
+       if ($now =~ /[A-Z]/) {
+               $seen .= $now;
+       } elsif ($now eq '+') {
+               my $ndir;
+               $ndir = 0 if $map[$y-1][$x] ne ' ' && $dir != 2;
+               $ndir = 1 if $map[$y][$x+1] ne ' ' && $dir != 3;
+               $ndir = 2 if $map[$y+1][$x] ne ' ' && $dir != 0;
+               $ndir = 3 if $map[$y][$x-1] ne ' ' && $dir != 1;
+               $dir = $ndir;
+       }
+       if ($dir == 0) {
+               $y--;
+       } elsif ($dir == 1) {
+               $x++;
+       } elsif ($dir == 2) {
+               $y++;
+       } else {
+               $x--;
+       }
+       last if $x < 0 || $y < 0 || $x > $xmax || $y > $ymax || $map[$y][$x] eq ' ';
+}
+
+say $seen;
+