Advent of Code 2024 - Day 07

Mix.install([{:kino, github: "livebook-dev/kino"}])

kino_input = Kino.Input.textarea("Please paste your input file: ")

Part 1

input = Kino.Input.read(kino_input)

input
|> String.split("\n", trim: true)
|> Enum.map(fn equation ->
  equation
  |> String.split(": ")
  |> then(fn [test_value, numbers] ->
    {
      String.to_integer(test_value),
      numbers
      |> String.split()
      |> Enum.map(&String.to_integer/1)
    }
  end)
end)
|> Enum.filter(fn {test_value, numbers} ->
  Enum.reduce(tl(numbers), [hd(numbers)], fn next, acc ->
    Enum.flat_map(acc, fn current ->
      [
        current + next,
        current * next,
      ]
    end)
  end)
  |> Enum.member?(test_value)
end)
|> Enum.reduce(0, fn {test_value, _}, acc ->
  acc + test_value
end)

Part 2

input = Kino.Input.read(kino_input)

defmodule Shifter do
  def shift(a, 0), do: a
  def shift(a, b), do: shift(a * 10, div(b, 10))
end

input
|> String.split("\n", trim: true)
|> Enum.map(fn equation ->
  equation
  |> String.split(": ")
  |> then(fn [test_value, numbers] ->
    {
      String.to_integer(test_value),
      numbers
      |> String.split()
      |> Enum.map(&String.to_integer/1)
    }
  end)
end)
|> Enum.filter(fn {test_value, numbers} ->
  Enum.reduce(tl(numbers), [hd(numbers)], fn next, acc ->
    Enum.flat_map(acc, fn current ->
      [
        current + next,
        current * next,
        Shifter.shift(current, next) + next,
      ]
    end)
  end)
  |> Enum.member?(test_value)
end)
|> Enum.reduce(0, fn {test_value, _}, acc ->
  acc + test_value
end)