This is a solution to Advent of Code 2020 day 11, written in Raku.
https://adventofcode.com/2020/day/11
Part One
Simulate your seating area by applying the seating rules repeatedly until no seats change state. How many seats end up occupied?
Raku
my @plan[97;98] = '11-input.txt'.IO.lines.map(*.comb);
my @new[97;98];
sub check($y, $x) {
if $y < 0 or $y > 96 or $x < 0 or $x > 97 {
return False
} elsif @plan[$y;$x] eq '#' {
return True
} else {
return False
}
}
sub check-neighbours($y, $x) {
(check($y-1, $x-1), check($y-1, $x), check($y-1,$x+1),
check($y, $x-1), check($y,$x+1),
check($y+1, $x-1), check($y+1, $x), check($y+1,$x+1))
}
sub iteration {
for ^97 -> $y {
for ^98 -> $x {
given @plan[$y;$x] {
when '.' {
@new[$y;$x] = '.'
}
when 'L' {
if ([+] check-neighbours($y, $x)) == 0 {
@new[$y;$x] = '#'
} else {
@new[$y;$x] = 'L'
}
}
when '#' {
if ([+] check-neighbours($y, $x)) > 3 {
@new[$y;$x] = 'L'
} else {
@new[$y;$x] = '#'
}
}
}
}
}
}
sub show {
for ^97 -> $y {
for ^98 -> $x { print @new[$y;$x]; }
say '';
}
}
sub count {
my $n = 0;
for ^97 -> $y {
for ^98 -> $x { $n += (@new[$y;$x] eq '#') ?? 1 !! 0 }
}
$n;
}
for ^110 -> $n {
say "iteration {$n}";
iteration;
show;
if @new ~~ @plan {
say 'Steady state';
exit;
} else {
for ^97 -> $y {
for ^98 -> $x {
@plan[$y;$x] = @new[$y;$x];
}
}
}
}
say count;Part Two
Given the new visibility method and the rule change for occupied seats becoming empty, once equilibrium is reached, how many seats end up occupied?
Raku
my @plan[97;98] = '11-input.txt'.IO.lines.map(*.comb);
my @new[97;98];
sub check($y, $dy, $x, $dx) {
my $y1 = $y + $dy; my $x1 = $x + $dx;
if $y1 < 0 or $y1 > 96 or $x1 < 0 or $x1 > 97 {
return False
}
given @plan[$y1;$x1] {
when '#' {
return True
}
when 'L' {
return False
}
when '.' {
return check($y1, $dy, $x1, $dx)
}
}
}
sub check-neighbours($y, $x) {
(check($y, -1, $x, -1), check($y, -1, $x, 0), check($y, -1, $x, +1),
check($y, 0, $x, -1), check($y, 0, $x, +1),
check($y, +1, $x, -1), check($y, +1, $x, 0), check($y, +1,$x, +1))
}
sub iteration {
for ^97 -> $y {
for ^98 -> $x {
given @plan[$y;$x] {
when '.' {
@new[$y;$x] = '.'
}
when 'L' {
if ([+] check-neighbours($y, $x)) == 0 {
@new[$y;$x] = '#'
} else {
@new[$y;$x] = 'L'
}
}
when '#' {
if ([+] check-neighbours($y, $x)) > 4 {
@new[$y;$x] = 'L'
} else {
@new[$y;$x] = '#'
}
}
}
}
}
}
sub show {
my $n = 0;
for ^97 -> $y {
for ^98 -> $x {
$n += (@new[$y;$x] eq '#') ?? 1 !! 0;
#print @new[$y;$x];
}
#say '';
}
say $n;
}
for ^100 -> $n {
say "iteration {$n}";
iteration;
show;
if @new ~~ @plan {
say 'Steady state';
exit;
} else {
for ^97 -> $y {
for ^98 -> $x {
@plan[$y;$x] = @new[$y;$x];
}
}
}
}iteration 0 7788 iteration 1 4 iteration 2 7776 iteration 3 12 iteration 4 7752 iteration 5 24 iteration 6 7716 iteration 7 41 iteration 8 7670 iteration 9 59 iteration 10 7614 iteration 11 84 iteration 12 7545 iteration 13 113 iteration 14 7464 iteration 15 143 iteration 16 7372 iteration 17 183 iteration 18 7262 iteration 19 229 iteration 20 7136 iteration 21 274 iteration 22 7002 iteration 23 327 iteration 24 6857 iteration 25 385 iteration 26 6704 iteration 27 449 iteration 28 6540 iteration 29 516 iteration 30 6362 iteration 31 579 iteration 32 6188 iteration 33 654 iteration 34 5987 iteration 35 733 iteration 36 5768 iteration 37 817 iteration 38 5545 iteration 39 902 iteration 40 5326 iteration 41 994 iteration 42 5085 iteration 43 1083 iteration 44 4849 iteration 45 1181 iteration 46 4605 iteration 47 1267 iteration 48 4402 iteration 49 1354 iteration 50 4188 iteration 51 1430 iteration 52 3994 iteration 53 1507 iteration 54 3819 iteration 55 1578 iteration 56 3641 iteration 57 1640 iteration 58 3482 iteration 59 1696 iteration 60 3334 iteration 61 1756 iteration 62 3195 iteration 63 1815 iteration 64 3061 iteration 65 1866 iteration 66 2929 iteration 67 1920 iteration 68 2806 iteration 69 1964 iteration 70 2700 iteration 71 2012 iteration 72 2590 iteration 73 2048 iteration 74 2496 iteration 75 2081 iteration 76 2407 iteration 77 2107 iteration 78 2346 iteration 79 2132 iteration 80 2289 iteration 81 2153 iteration 82 2247 iteration 83 2172 iteration 84 2209 iteration 85 2183 iteration 86 2192 iteration 87 2190 iteration 88 2190 iteration 89 2190 iteration 90 2190 iteration 91 2190 iteration 92 2190 iteration 93 2190 iteration 94 2190 iteration 95 2190 iteration 96 2190 iteration 97 2190 iteration 98 2190 iteration 99 2190