day-16-star-2.pl

#!/usr/bin/perl
use warnings;
use 5.036;

chomp(my @lines = <>);

my @map = map { [ split(//, $_) ] } @lines;
my $max = 0;

for my $i (0..$#{$map[0]}) {
    my $count = &countTiles($i, 0, 0b0010);
    $max = $max > $count ? $max : $count;
    $count = &countTiles($i, $#map, 0b1000);
    $max = $max > $count ? $max : $count;
}

for my $i (0..$#map) {
    my $count = &countTiles(0, $i, 0b0001);
    $max = $max > $count ? $max : $count;
    $count = &countTiles($#{$map[0]}, $i, 0b0100);
    $max = $max > $count ? $max : $count;
}

say $max;

sub countTiles($startX, $startY, $startDir) {
    my @energyMap = map { [ map { 0 } @{$_} ] } @map;
    my %beamsStarted;

    # say "@{$map[0]}";
    # say "@{$energyMap[0]}";

    # beam: { x, y, dir }
    # right = 0001,
    # down = 0010,
    # left = 0100,
    # up = 1000

    my @beams = ( { 'x' => $startX, 'y' => $startY, 'dir' => $startDir } );

    while (@beams) {
        my %beam = %{shift @beams};

        # say "New beam - x: $beam{'x'}, y: $beam{'y'}, dir: $beam{'dir'}";

        # foreach my $b (@beams) {
        #     say "x: %{$b}{'x'}, y: %{$b}{'y'}, dir: %{$b}{'dir'}";
        # }

        while (1) {
            my $nextTile = $map[$beam{'y'}][$beam{'x'}];

            last unless $beam{'y'} >= 0 && $beam{'x'} >= 0;
            last unless $nextTile;

            # say "x: $beam{'x'}, y: $beam{'y'}, dir: $beam{'dir'}, next tile: $nextTile";

            if ($nextTile eq '.') {
                $energyMap[$beam{'y'}][$beam{'x'}] = 1;
                (my $x, my $y) = &moveDir(\%beam);
                $beam{'x'} = $x;
                $beam{'y'} = $y;
            } elsif ($nextTile eq '/') {
                $energyMap[$beam{'y'}][$beam{'x'}] = 1;
                $beam{'dir'} = &mirrorDir($beam{'dir'}, '/');
                (my $x, my $y) = &moveDir(\%beam);
                $beam{'x'} = $x;
                $beam{'y'} = $y;
            } elsif ($nextTile eq '\\') {
                $energyMap[$beam{'y'}][$beam{'x'}] = 1;
                $beam{'dir'} = &mirrorDir($beam{'dir'}, '\\');
                (my $x, my $y) = &moveDir(\%beam);
                $beam{'x'} = $x;
                $beam{'y'} = $y;
            } elsif ($nextTile eq '|') {
                if ($beam{'dir'} == 0b0010 || $beam{'dir'} == 0b1000) {
                    $energyMap[$beam{'y'}][$beam{'x'}] = 1;
                    (my $x, my $y) = &moveDir(\%beam);
                    $beam{'x'} = $x;
                    $beam{'y'} = $y;
                } elsif ($beam{'dir'} == 0b0100 || $beam{'dir'} == 0b0001) {
                    $energyMap[$beam{'y'}][$beam{'x'}] = 1;
                    &tryStartBeam(\@beams, \%beamsStarted, $beam{'x'}, $beam{'y'} - 1, 0b1000);
                    &tryStartBeam(\@beams, \%beamsStarted, $beam{'x'}, $beam{'y'} + 1, 0b0010);
                    last;
                }
            } elsif ($nextTile eq '-') {
                if ($beam{'dir'} == 0b0010 || $beam{'dir'} == 0b1000) {
                    $energyMap[$beam{'y'}][$beam{'x'}] = 1;
                    &tryStartBeam(\@beams, \%beamsStarted, $beam{'x'} + 1, $beam{'y'}, 0b0001);
                    &tryStartBeam(\@beams, \%beamsStarted, $beam{'x'} - 1, $beam{'y'}, 0b0100);
                    last;
                } elsif ($beam{'dir'} == 0b0100 || $beam{'dir'} == 0b0001) {
                    $energyMap[$beam{'y'}][$beam{'x'}] = 1;
                    (my $x, my $y) = &moveDir(\%beam);
                    $beam{'x'} = $x;
                    $beam{'y'} = $y;
                }
            } else {
                die "Unknown tile: $nextTile";
            }
        }
    }

    my $sum = 0;
    foreach my $lineRef (@energyMap) {
        # say "@{$lineRef}";
        foreach my $v (@{$lineRef}) {
            $sum += $v;
        }
    }
    return $sum;
    # say $sum;
}

sub tryStartBeam($beamsRef, $beamsStartedRef, $x, $y, $dir) {
    my $hash = $x . $y . $dir;
    unless ($$beamsStartedRef{$hash}) {
        $$beamsStartedRef{$hash} = 1;
        push(@{$beamsRef}, { 'x' => $x, 'y' => $y, 'dir' => $dir });
    }
}

sub moveDir($beamRef) {
    (my $x, my $y, my $dir) = (${$beamRef}{'x'}, ${$beamRef}{'y'}, ${$beamRef}{'dir'});
    if ($dir == 0b0001) {
        return ($x + 1, $y);
    } elsif ($dir == 0b0010) {
        return ($x, $y + 1);
    } elsif ($dir == 0b0100) {
        return ($x - 1, $y);
    } elsif ($dir == 0b1000) {
        return ($x, $y - 1);
    } else {
        die "Unknown dir: $dir";
    }
}

sub mirrorDir($dir, $mirror) {
    if ($mirror eq '/') {
        if ($dir == 0b0001) {
            return 0b1000;
        } elsif ($dir == 0b0010) {
            return 0b0100;
        } elsif ($dir == 0b0100) {
            return 0b0010;
        } elsif ($dir == 0b1000) {
            return 0b0001;
        } else {
            die "Unknown dir: $dir in mirror: $mirror";
        }
    } elsif ($mirror eq '\\') {
        if ($dir == 0b0001) {
            return 0b0010;
        } elsif ($dir == 0b0010) {
            return 0b0001;
        } elsif ($dir == 0b0100) {
            return 0b1000;
        } elsif ($dir == 0b1000) {
            return 0b0100;
        } else {
            die "Unknown dir: $dir in mirror: $mirror";
        }
    } else {
        die "Unknown mirror: $mirror";
    }
}