Day12

Mix.install([
  {:kino, "~> 0.11.0"},
  {:memoize, "~>1.4.2"}
])

Section

input = Kino.Input.textarea("Input")

defmodule Springs do
  use Memoize

  defmemo(fit(<<>>, parts) when length(parts) > 0, do: 0)

  defmemo(fit(pattern, []), do: if(String.contains?(pattern, "#"), do: 0, else: 1))

  defmemo(fit(<<?., pattern::binary>>, parts), do: fit(pattern, parts))

  defmemo fit(pattern, [p | parts]) do
    case pattern do
      <<?#, _part::binary-size(p - 1), ?#, _pattern::binary>> ->
        0

      <<??, part::binary-size(p - 1), ?#, pattern::binary>> ->
        fit(part <> "#" <> pattern, [p | parts])

      <<part::binary-size(p)>> ->
        if not String.contains?(part, ".") and parts == [], do: 1, else: 0

      <<?#, part::binary-size(p - 1), _next::binary-size(1), pattern::binary>> ->
        if String.contains?(part, "."), do: 0, else: fit(pattern, parts)

      <<??, part::binary-size(p - 1), next::binary-size(1), pattern::binary>> ->
        if String.contains?(part, ".") do
          fit(part <> next <> pattern, [p | parts])
        else
          fit(pattern, parts) + fit(part <> next <> pattern, [p | parts])
        end

      _pattern ->
        0
    end
  end
end

input
|> Kino.Input.read()
|> String.split(["\n", " "])
|> Enum.chunk_every(2)
|> Enum.map(fn [pattern, parts] ->
  {parts, _} = Code.eval_string("[" <> parts <> "]")
  Springs.fit(pattern, parts)
end)
|> Enum.sum()

input
|> Kino.Input.read()
|> String.split(["\n", " "])
|> Enum.chunk_every(2)
|> Enum.map(fn [pattern, parts] ->
  pattern = pattern |> List.duplicate(5) |> Enum.join("?")
  {parts, _} = Code.eval_string("[" <> parts <> "]")
  Springs.fit(pattern, List.flatten(List.duplicate(parts, 5)))
end)
|> Enum.sum()