Rest of 2019

[aoc.git] / 2019 / 47.pl

diff --git a/2019/47.pl b/2019/47.pl
new file mode 100755 (executable)
index 0000000..c02aaf9
--- /dev/null
+++ b/2019/47.pl
@@ -0,0 +1,43 @@
+#!/usr/bin/perl -w
+
+use v5.16;
+
+my @map = map { chomp; [ split // ] } <>;
+
+my $min;
+my %seen;
+while (1) {
+       say "After ", ++$min, ":";
+       my @nm;
+       for my $y (0 .. 4) {
+       for my $x (0 .. 4) {
+               my $sum = 0;
+               for my ($dx, $dy) (1, 0, 0, 1, -1, 0, 0, -1) {
+                       my $nx = $x + $dx;
+                       my $ny = $y + $dy;
+                       next if $nx < 0 || $nx > 4 || $ny < 0 || $ny > 4;
+                       $sum++ if $map[$ny][$nx] eq '#';
+               }
+               # say "at $x $y neigbors $sum";
+               if ($map[$y][$x] eq '#') {
+                       $nm[$y][$x] = $sum == 1 ? '#' : '.';
+               } else {
+                       $nm[$y][$x] = $sum == 1 || $sum == 2 ? '#' : '.';
+               }
+               print $nm[$y][$x];
+       }
+               print "\n";
+       }
+       @map = @nm;
+       my $key = join('', map { join('', @$_) } @map);
+       if ($seen{$key}) {
+               say "this one was last seen at min $seen{$key}";
+               my $b = reverse $key;
+               $b =~ tr/.#/01/;
+               say oct "0b$b";
+               last;
+       }
+       $seen{$key} = $min;
+       print "\n";
+}
+