Day 11

[aoc2020.git] / 21.pl

diff --git a/21.pl b/21.pl
new file mode 100755 (executable)
index 0000000..4a3d0ba
--- /dev/null
+++ b/21.pl
@@ -0,0 +1,55 @@
+#!/usr/bin/perl -w
+
+use strict;
+
+my @seats = map { chomp; [ split // ] } (<>);
+
+my $cols = @{ $seats[0] };
+my $rows = @seats;
+
+print "$cols x $rows\n";
+
+while (1) {
+       my $was_change = 0;
+       my $occup = 0;
+       my @newseats;
+       for my $row (0 .. $rows-1) {
+               my @newrow;
+               for my $col (0 .. $cols-1) {
+                       my $neigh = '';
+                       for my $add ([-1, -1], [-1, 0], [-1, 1],
+                               [0, -1], [0, 1],
+                               [1, -1], [1, 0], [1, 1]) {
+                               my $row1 = $row + $add->[0];
+                               my $col1 = $col + $add->[1];
+                               next if $row1 >= $rows || $row1 < 0
+                                       || $col1 >= $cols || $col1 < 0;
+                               $neigh .= $seats[$row1]->[$col1];
+                       }
+                       my $neigh_empty =()= $neigh =~ /L/g;
+                       my $neigh_occup =()= $neigh =~ /#/g;
+
+                       if ($seats[$row]->[$col] eq 'L' && !$neigh_occup) {
+                               push @newrow, '#';
+                               $was_change = 1;
+                               $occup++;
+                       } elsif ($seats[$row]->[$col] eq '#' && $neigh_occup >= 4) {
+                               push @newrow, 'L';
+                               $was_change = 1;
+                       } else {
+                               push @newrow, $seats[$row]->[$col];
+                               $occup++ if $seats[$row]->[$col] eq '#';
+                       }
+               }
+               push @newseats, \@newrow;
+       }
+       @seats = @newseats;
+       #for my $row (@seats) {
+       #       print @$row, "\n";
+       #}
+       print "$occup occupied seats\n";
+       # print "\n";
+       last if !$was_change;
+}
+
+