Day 13

Mix.install([
  {:pythonx, "~> 0.2.5"}
])

Setup

input =
  System.fetch_env!("LB_AOC_DIR")
  |> Path.join("data/day13.txt")
  |> File.read!()

nil

nil

Solve

sample = """
Button A: X+94, Y+34
Button B: X+22, Y+67
Prize: X=8400, Y=5400

Button A: X+26, Y+66
Button B: X+67, Y+21
Prize: X=12748, Y=12176

Button A: X+17, Y+86
Button B: X+84, Y+37
Prize: X=7870, Y=6450

Button A: X+69, Y+23
Button B: X+27, Y+71
Prize: X=18641, Y=10279
"""

"Button A: X+94, Y+34\nButton B: X+22, Y+67\nPrize: X=8400, Y=5400\n\nButton A: X+26, Y+66\nButton B: X+67, Y+21\nPrize: X=12748, Y=12176\n\nButton A: X+17, Y+86\nButton B: X+84, Y+37\nPrize: X=7870, Y=6450\n\nButton A: X+69, Y+23\nButton B: X+27, Y+71\nPrize: X=18641, Y=10279\n"

parse = fn input ->
  for block <- String.split(input, "\n\n"), block != "" do
    for part <- String.split(block, "\n"), part != "", reduce: %{} do
      acc ->
        [prefix, post] = String.split(part, ":")

        case prefix do
          "Prize" ->
            [<<"X=", x::binary>>, <<"Y=", y::binary>>] =
              String.split(post, ",") |> Enum.map(&amp;String.trim/1)

            acc
            |> Map.put(:prize, {String.to_integer(x), String.to_integer(y)})

          <<"Button ", button::binary>> ->
            [<<"X+", x::binary>>, <<"Y+", y::binary>>] =
              String.split(post, ",") |> Enum.map(&amp;String.trim/1)

            button = String.downcase(button)

            acc
            |> Map.put(String.to_atom(button), {String.to_integer(x), String.to_integer(y)})
        end
    end
  end
end

#Function<42.39164016/1 in :erl_eval.expr/6>

parse.(sample)

[
  %{b: {22, 67}, a: {94, 34}, prize: {8400, 5400}},
  %{b: {67, 21}, a: {26, 66}, prize: {12748, 12176}},
  %{b: {84, 37}, a: {17, 86}, prize: {7870, 6450}},
  %{b: {27, 71}, a: {69, 23}, prize: {18641, 10279}}
]

Pythonx.initialize_once("/Library/Frameworks/Python.framework/Versions/3.11/bin/python3")

:ok

import Pythonx
pip! ["install", "-U", "scipy"]

{%IO.Stream{device: :standard_io, raw: false, line_or_bytes: :line}, 134}

defmodule Day13 do
  import Pythonx
  pip! ["install", "-U", "scipy"]
  def linsolve(%{a: {ax, ay}, b: {bx, by}, prize: {px, py}}) do
    c = [3, 1]
    a = [[ax, bx], [ay, by]]
    b = [px, py]

    pyeval(
      """
      from scipy.optimize import linprog
      solution = linprog(
              c,
              A_eq=a,
              b_eq=b,
              integrality=1,
              options={"autoscale": True, "presolve": False},
      )
      x = solution.x
      # print(solution)
      # if solution.success:
      #   x = solution.x
      # else:
      #   x = []
      """,
      return: [:x]
    )
    x
  end

  @doc ~S"""
  iex> Day13.part1("Button A: X+94, Y+34\nButton B: X+22, Y+67\nPrize: X=8400, Y=5400\n\nButton A: X+26, Y+66\nButton B: X+67, Y+21\nPrize: X=12748, Y=12176\n\nButton A: X+17, Y+86\nButton B: X+84, Y+37\nPrize: X=7870, Y=6450\n\nButton A: X+69, Y+23\nButton B: X+27, Y+71\nPrize: X=18641, Y=10279\n")
  480
  """
  def part1(input) do
    nil
  end

  @doc ~S"""
  iex> Day13.part2("Button A: X+94, Y+34\nButton B: X+22, Y+67\nPrize: X=8400, Y=5400\n\nButton A: X+26, Y+66\nButton B: X+67, Y+21\nPrize: X=12748, Y=12176\n\nButton A: X+17, Y+86\nButton B: X+84, Y+37\nPrize: X=7870, Y=6450\n\nButton A: X+69, Y+23\nButton B: X+27, Y+71\nPrize: X=18641, Y=10279\n")
  1206
  """
  def part2(input) do
    nil
  end
end

warning: variable "a" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ Documents/aoc2024/day13.livemd#cell:kdfsu4agkik32lgx:6: Day13.linsolve/1

warning: variable "b" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ Documents/aoc2024/day13.livemd#cell:kdfsu4agkik32lgx:7: Day13.linsolve/1

warning: variable "c" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ Documents/aoc2024/day13.livemd#cell:kdfsu4agkik32lgx:5: Day13.linsolve/1

warning: variable "input" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ Documents/aoc2024/day13.livemd#cell:kdfsu4agkik32lgx:35: Day13.part1/1

warning: variable "input" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ Documents/aoc2024/day13.livemd#cell:kdfsu4agkik32lgx:43: Day13.part2/1

{:module, Day13, <<70, 79, 82, 49, 0, 0, 10, ...>>, {:part2, 1}}

a = parse.(sample) |> hd

%{b: {22, 67}, a: {94, 34}, prize: {8400, 5400}}

Day13.linsolve(a)

pyinline("a = [i for i in range(10)]", return: [:a])

[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]]