2021 day9 part 2

This commit is contained in:
Adam Millerchip 2022-11-29 21:35:23 +09:00
parent 615f7cef3c
commit fb87183a6f
2 changed files with 36 additions and 3 deletions

1
.gitignore vendored
View file

@ -1,2 +1,3 @@
input
sample
arena

View file

@ -19,8 +19,40 @@ defmodule Day9 do
Enum.all?(neighbours(cave, x, y), fn {xn, yn} -> here < cave.floor[{xn, yn}] end)
end
def part2(_input) do
:ok
def part2(cave) do
cave
|> remove_nines()
|> find_basins()
|> Enum.sort(:desc)
|> Enum.take(3)
|> Enum.reduce(&Kernel.*/2)
end
defp find_basins(%Cave{floor: floor}) when floor == %{}, do: []
defp find_basins(cave) do
{cave, location} = get_start_location(cave)
{cave, basin} = find_basin(cave, [location], [location])
[basin | find_basins(cave)]
end
defp find_basin(cave, [], basin), do: {cave, length(basin)}
defp find_basin(cave, [{x, y} | locations], basin) do
neighbours = cave.floor |> Map.take(neighbours(cave, x, y)) |> Map.keys()
cave = %Cave{cave | floor: Map.drop(cave.floor, neighbours)}
find_basin(cave, locations ++ neighbours, basin ++ neighbours)
end
defp remove_nines(cave) do
floor = cave.floor |> Enum.reject(&match?({_k, 9}, &1)) |> Map.new()
%Cave{cave | floor: floor}
end
defp get_start_location(cave) do
[{location, _v}] = Enum.take(cave.floor, 1)
cave = %Cave{cave | floor: Map.delete(cave.floor, location)}
{cave, location}
end
def input do
@ -76,4 +108,4 @@ defmodule Day9 do
end
end
# Day9.run()
Day9.run()