49.pl

   1 #!/usr/bin/perl -w
   2
   3 use v5.16;
   4
   5 my @m = map { chomp; [ split // ] } <>;
   6
   7 my $xmax = @{ $m[0] };
   8 my $ymax = @m;
   9
  10 sub print_map {
  11         my $m = shift;
  12         for my $row (@m) {
  13                 say join('', @$row);
  14         }
  15         say "";
  16 }
  17
  18 my $step;
  19 my $moved;
  20 do {
  21         $moved = 0;
  22         my @m1;
  23         for my $y (0 .. $ymax-1) {
  24                 for my $x (0 .. $xmax-1) {
  25                         if ($m[$y][$x] eq '>') {
  26                                 my $nx = $x+1;
  27                                 $nx = 0 if $nx >= $xmax;
  28                                 if ($m[$y][$nx] eq '.') {
  29                                         $m1[$y][$nx] = '>';
  30                                         $m1[$y][$x] = '.';
  31                                         $moved++;
  32                                 } else {
  33                                         $m1[$y][$x] = $m[$y][$x];
  34                                 }
  35                         } else {
  36                                 if (!defined $m1[$y][$x]) {
  37                                         $m1[$y][$x] = $m[$y][$x];
  38                                 }
  39                         }
  40                 }
  41         }
  42         @m = @m1;
  43         @m1 = ();
  44
  45         for my $y (0 .. $ymax-1) {
  46                 for my $x (0 .. $xmax-1) {
  47                         if ($m[$y][$x] eq 'v') {
  48                                 my $ny = $y+1;
  49                                 $ny = 0 if $ny >= $ymax;
  50                                 if ($m[$ny][$x] eq '.') {
  51                                         $m1[$ny][$x] = 'v';
  52                                         $m1[$y][$x] = '.';
  53                                         $moved++;
  54                                 } else {
  55                                         $m1[$y][$x] = $m[$y][$x];
  56                                 }
  57                         } else {
  58                                 if (!defined $m1[$y][$x]) {
  59                                         $m1[$y][$x] = $m[$y][$x];
  60                                 }
  61                         }
  62                 }
  63         }
  64         @m = @m1;
  65         $step++;
  66         print_map(\@m);
  67 } while ($moved);
  68
  69 say "$step steps";
  70