Day 12

Mix.install([
  {:kino, "~> 0.7.0"}
])

IEx.Helpers.c("/Users/johnb/dev/2023adventOfCode/advent_of_code.ex")
alias AdventOfCode, as: AOC
alias Kino.Input

# Note: when making the next template, something like this works well:
#   `cat day04.livemd | sed 's/03/04/' > day04.livemd`
#

Installation and Data

input_p1example = Kino.Input.textarea("Example Data")

input_p1puzzleInput = Kino.Input.textarea("Puzzle Input")

input_source_select =
  Kino.Input.select("Source", [{:example, "example"}, {:puzzle_input, "puzzle input"}])

p1data = fn ->
  (Kino.Input.read(input_source_select) == :example &&
     Kino.Input.read(input_p1example)) ||
    Kino.Input.read(input_p1puzzleInput)
end

Part 1

defmodule Day12 do
  def damaged_run_lengths(record) do
    record
    |> String.split(~r/[^#]/, trim: true)
    |> Enum.map(&String.length/1)
  end

  def matching_permutations(required_run_lengths, chars, prev_chars \\ "")

  def matching_permutations(required_run_lengths, [char], prev_chars) do
    if char == "?" do
      if damaged_run_lengths(prev_chars <> ".") == required_run_lengths ||
           damaged_run_lengths(prev_chars <> "#") == required_run_lengths do
        # IO.puts("match? '#{prev_chars <> "."}' or '#{prev_chars <> "#"}'")
        1
      else
        0
      end
    else
      if damaged_run_lengths(prev_chars <> char) == required_run_lengths do
        # IO.puts("match: #{prev_chars <> char}")
        1
      else
        0
      end
    end
  end

  def matching_permutations(required_run_lengths, [char | rest], prev_chars) do
    case char do
      "?" ->
        matching_permutations(required_run_lengths, rest, prev_chars <> ".") +
          matching_permutations(required_run_lengths, rest, prev_chars <> "#")

      _ ->
        matching_permutations(required_run_lengths, rest, prev_chars <> char)
    end
  end

  def solve(text) do
    text
    |> AOC.as_single_lines()
    |> Enum.map(fn line ->
      [record, required_run_lengths] = String.split(line, " ", trim: true)
      # |> IO.inspect()

      required_run_lengths =
        required_run_lengths
        |> String.split(",", trim: true)
        |> Enum.map(fn digits -> digits |> String.to_integer() end)

      # |> IO.inspect(label: "'#{record}' .vs #{inspect(damaged_run_lengths(record))}")

      chars = String.split(record, "", trim: true)

      matching_permutations(required_run_lengths, chars)
      |> IO.inspect(label: "matching_permutations")
    end)
    |> Enum.sum()
  end

  def solve2(text) do
    text
    |> AOC.as_single_lines()
    |> Enum.map(fn line ->
      [record, required_run_lengths] = String.split(line, " ", trim: true)
      # |> IO.inspect()

      run_lengths =
        required_run_lengths
        |> String.split(",", trim: true)
        |> Enum.map(fn digits -> digits |> String.to_integer() end)

      # |> IO.inspect(label: "'#{record}' .vs #{inspect(damaged_run_lengths(record))}")

      record = Enum.join([record, record, record, record, record], "?")

      required_run_lengths =
        run_lengths ++ run_lengths ++ run_lengths ++ run_lengths ++ run_lengths

      IO.puts(record)
      IO.inspect(required_run_lengths)

      chars = String.split(record, "", trim: true)

      matching_permutations(required_run_lengths, chars)
      |> IO.inspect(label: "matching_permutations")
    end)
    |> Enum.sum()
  end
end

p1data.()
|> Day12.solve()
|> IO.inspect(label: "\n*** Part 1 solution (example: 21)")

# 7633

p1data.()
|> Day12.solve2()
|> IO.inspect(label: "\n*** Part 2 solution (example: 525152)")

#