21.pl

   1 #!/usr/bin/perl -w
   2
   3 use strict;
   4
   5 my @seats = map { chomp; [ split // ] } (<>);
   6
   7 my $cols = @{ $seats[0] };
   8 my $rows = @seats;
   9
  10 print "$cols x $rows\n";
  11
  12 while (1) {
  13         my $was_change = 0;
  14         my $occup = 0;
  15         my @newseats;
  16         for my $row (0 .. $rows-1) {
  17                 my @newrow;
  18                 for my $col (0 .. $cols-1) {
  19                         my $neigh = '';
  20                         for my $add ([-1, -1], [-1, 0], [-1, 1],
  21                                 [0, -1], [0, 1],
  22                                 [1, -1], [1, 0], [1, 1]) {
  23                                 my $row1 = $row + $add->[0];
  24                                 my $col1 = $col + $add->[1];
  25                                 next if $row1 >= $rows || $row1 < 0
  26                                         || $col1 >= $cols || $col1 < 0;
  27                                 $neigh .= $seats[$row1]->[$col1];
  28                         }
  29                         my $neigh_empty =()= $neigh =~ /L/g;
  30                         my $neigh_occup =()= $neigh =~ /#/g;
  31
  32                         if ($seats[$row]->[$col] eq 'L' && !$neigh_occup) {
  33                                 push @newrow, '#';
  34                                 $was_change = 1;
  35                                 $occup++;
  36                         } elsif ($seats[$row]->[$col] eq '#' && $neigh_occup >= 4) {
  37                                 push @newrow, 'L';
  38                                 $was_change = 1;
  39                         } else {
  40                                 push @newrow, $seats[$row]->[$col];
  41                                 $occup++ if $seats[$row]->[$col] eq '#';
  42                         }
  43                 }
  44                 push @newseats, \@newrow;
  45         }
  46         @seats = @newseats;
  47         #for my $row (@seats) {
  48         #       print @$row, "\n";
  49         #}
  50         print "$occup occupied seats\n";
  51         # print "\n";
  52         last if !$was_change;
  53 }
  54
  55