Day 8: Resonant Collinearity
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FAQ
- What is this?: Here is a post with a large amount of details: https://programming.dev/post/6637268
- Where do I participate?: https://adventofcode.com/
- Is there a leaderboard for the community?: We have a programming.dev leaderboard with the info on how to join in this post: https://programming.dev/post/6631465
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1 point
Raku
Solution
sub MAIN($input) {
my $file = open $input;
my @map = $file.slurp.lines>>.comb>>.List.List;
my %freqs;
for 0..^@map.elems -> $row {
for 0..^@map[0].elems -> $col {
if @map[$row; $col] ne "." {
my $freq = @map[$row; $col];
%freqs{$freq} = [] if %freqs{$freq}:!exists;
%freqs{$freq}.push(($row, $col));
}
}
}
my %antinodes is SetHash;
for %freqs.kv -> $freq, @locations {
for (0..^@locations.elems) X (0..^@locations.elems) -> ($loc1, $loc2) {
next if $loc1 == $loc2;
my @base = @locations[$loc1].List;
my @vector = @locations[$loc2].List Z- @base;
my @antinode1 = @base Z+ @vector.map(* * 2);
%antinodes{@antinode1.List.raku}++ if point-is-in-map(@map, @antinode1);
my @antinode2 = @base Z+ @vector.map(* * -1);
%antinodes{@antinode2.List.raku}++ if point-is-in-map(@map, @antinode2);
}
}
my $part1-solution = %antinodes.elems;
say "part 1: $part1-solution";
my %antinodes2 is SetHash;
for %freqs.kv -> $freq, @locations {
for (0..^@locations.elems) X (0..^@locations.elems) -> ($loc1, $loc2) {
next if $loc1 == $loc2;
my @base = @locations[$loc1].List;
my @vector = @locations[$loc2].List Z- @base;
# make integer unit-ish vector
for 2..@vector[0] -> $divisor {
if @vector[0] %% $divisor and @vector[1] %% $divisor {
@vector[0] = @vector[0] div $divisor;
@vector[1] = @vector[1] div $divisor;
}
}
for 0..max(@map.elems, @map[0].elems) -> $length {
my @antinode = @base Z+ @vector.map(* * $length);
if point-is-in-map(@map, @antinode) {
%antinodes2{@antinode.List.raku}++
} else {
last
}
}
for 1..max(@map.elems, @map[0].elems) -> $length {
my @antinode = @base Z+ @vector.map(* * -$length);
if point-is-in-map(@map, @antinode) {
%antinodes2{@antinode.List.raku}++
} else {
last
}
}
}
}
my $part2-solution = %antinodes2.elems;
say "part 2: $part2-solution";
}
sub point-is-in-map(@map, @point) {
return False if !(0 <= @point[0] < @map.elems);
return False if !(0 <= @point[1] < @map[0].elems);
return True;
}
