Day 24 - nice!

diff --git a/47.pl b/47.pl
new file mode 100755 (executable)
index 0000000..fca227f
--- /dev/null
+++ b/47.pl
@@ -0,0 +1,29 @@
+#!/usr/bin/perl -w
+
+use strict;
+
+my %tiles;
+
+while (<>) {
+       chomp;
+       my ($x, $y) = (0, 0);
+       while (length) {
+               s/\A(se|ne|sw|nw|e|w)//;
+               if ($1 eq 'ne') {
+                       $y++;
+               } elsif ($1 eq 'e') {
+                       $x++;
+               } elsif ($1 eq 'se') {
+                       $x++; $y--;
+               } elsif ($1 eq 'sw') {
+                       $y--;
+               } elsif ($1 eq 'w') {
+                       $x--;
+               } elsif ($1 eq 'nw') {
+                       $x--; $y++;
+               }
+       }
+       $tiles{"$x|$y"}++;
+}
+
+print "Tiles=" . (grep { $tiles{$_} % 2 == 1 } keys %tiles)."\n";

diff --git a/48.pl b/48.pl
new file mode 100755 (executable)
index 0000000..f76f993
--- /dev/null
+++ b/48.pl
@@ -0,0 +1,60 @@
+#!/usr/bin/perl -w
+
+use strict;
+
+my %tiles;
+
+my ($min_x, $max_x, $min_y, $max_y);
+
+while (<>) {
+       chomp;
+       my ($x, $y) = (0, 0);
+       while (length) {
+               s/\A(se|ne|sw|nw|e|w)//;
+               if ($1 eq 'ne') {
+                       $y++;
+               } elsif ($1 eq 'e') {
+                       $x++;
+               } elsif ($1 eq 'se') {
+                       $x++; $y--;
+               } elsif ($1 eq 'sw') {
+                       $y--;
+               } elsif ($1 eq 'w') {
+                       $x--;
+               } elsif ($1 eq 'nw') {
+                       $x--; $y++;
+               }
+       }
+       $tiles{"$x|$y"} ^= 1;
+       $min_x = $x if !defined $min_x || $min_x > $x;
+       $max_x = $x if !defined $max_x || $max_x < $x;
+       $min_y = $y if !defined $min_y || $min_y > $y;
+       $max_y = $y if !defined $max_y || $max_y < $y;
+}
+
+
+for (1 .. 100) {
+       $min_x--; $min_y--; $max_x++, $max_y++;
+       my %newtiles;
+       for my $x ($min_x .. $max_x) {
+       for my $y ($min_y .. $max_y) {
+               my $count = 0;
+               $count++ if $tiles{($x+1).'|'.($y)}; # E
+               $count++ if $tiles{($x).'|'.($y+1)}; # NE
+               $count++ if $tiles{($x+1).'|'.($y-1)}; # SE
+               $count++ if $tiles{($x).'|'.($y-1)}; # SW
+               $count++ if $tiles{($x-1).'|'.($y)}; # W
+               $count++ if $tiles{($x-1).'|'.($y+1)}; # NW
+               if ($tiles{"$x|$y"} && ($count == 0 || $count > 2)) {
+                       $newtiles{"$x|$y"} = 0;
+               } elsif (!$tiles{"$x|$y"} && $count == 2) {
+                       $newtiles{"$x|$y"} = 1;
+               } else {
+                       $newtiles{"$x|$y"} = $tiles{"$x|$y"};
+               }
+       }
+       }
+       %tiles = %newtiles;
+       print "Tiles=" . (grep { $tiles{$_} } keys %tiles)."\n";
+}
+