60 lines
1.7 KiB
Elixir
60 lines
1.7 KiB
Elixir
|
defmodule Day17Part1 do
|
||
|
|
def run do
|
||
|
|
File.read!("input")
|
||
|
|
|> String.split("\n", trim: true)
|
||
|
|
|> parse_input()
|
||
|
|
|> boot(6)
|
||
|
|
|> Enum.count()
|
||
|
|
|> IO.puts()
|
||
|
|
end
|
||
|
|
|
||
|
|
def parse_input(input) do
|
||
|
|
{_y, cubes} =
|
||
|
|
Enum.reduce(input, {0, MapSet.new()}, fn row, {y, cubes} ->
|
||
|
|
{_x, cubes} =
|
||
|
|
Enum.reduce(String.graphemes(row), {0, cubes}, fn
|
||
|
|
".", {x, cubes} -> {x + 1, cubes}
|
||
|
|
"#", {x, cubes} -> {x + 1, MapSet.put(cubes, {x, y, 0})}
|
||
|
|
end)
|
||
|
|
|
||
|
|
{y + 1, cubes}
|
||
|
|
end)
|
||
|
|
|
||
|
|
cubes
|
||
|
|
end
|
||
|
|
|
||
|
|
def boot(cubes, 0), do: cubes
|
||
|
|
def boot(cubes, count), do: boot(cycle(cubes), count - 1)
|
||
|
|
|
||
|
|
def cycle(cubes) do
|
||
|
|
{next_cubes, inactives} =
|
||
|
|
Enum.reduce(cubes, {MapSet.new(), MapSet.new()}, fn cube, {next_cubes, inactives} ->
|
||
|
|
{active_count, inactives} =
|
||
|
|
Enum.reduce(neighbours(cube), {0, inactives}, fn neighbour, {active_count, inactives} ->
|
||
|
|
if MapSet.member?(cubes, neighbour) do
|
||
|
|
{active_count + 1, inactives}
|
||
|
|
else
|
||
|
|
{active_count, MapSet.put(inactives, neighbour)}
|
||
|
|
end
|
||
|
|
end)
|
||
|
|
|
||
|
|
next_cubes = if active_count in 2..3, do: MapSet.put(next_cubes, cube), else: next_cubes
|
||
|
|
{next_cubes, inactives}
|
||
|
|
end)
|
||
|
|
|
||
|
|
Enum.reduce(inactives, next_cubes, fn inactive, next_cubes ->
|
||
|
|
active_neighbours =
|
||
|
|
inactive |> neighbours() |> MapSet.new() |> MapSet.intersection(cubes) |> Enum.count()
|
||
|
|
|
||
|
|
if active_neighbours == 3, do: MapSet.put(next_cubes, inactive), else: next_cubes
|
||
|
|
end)
|
||
|
|
end
|
||
|
|
|
||
|
|
def neighbours({x, y, z} = me) do
|
||
|
|
all = for x <- (x - 1)..(x + 1), y <- (y - 1)..(y + 1), z <- (z - 1)..(z + 1), do: {x, y, z}
|
||
|
|
all -- [me]
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
Day17Part1.run()
|