Advent of code 2021 - day 9 - part 1 - solution

advent-of-code-2021-day9-part-1.ex

defmodule Smoke do
  def read(path) do
    [h | t] =
      File.read!(path)
      |> String.split("\n")
      |> Enum.map(fn x ->
        String.codepoints(x)
        |> Enum.map(&String.to_integer/1)
        |> (fn x -> [10] ++ x ++ [10] end).()
      end)

    margin = List.duplicate(10, Enum.count(h))
    [margin] ++ [h | t] ++ [margin]
  end

  def check([[_, _ | t1] | _], acc) when t1 == [] do
    acc
  end

  def check([[_, b, c | t1], [d, e, f | t2], [_, h, i | t3]], acc) do
    case e < b and e < d and e < f and e < h do
      true -> check([[b, c | t1], [e, f | t2], [h, i | t3]], acc + e + 1)
      false -> check([[b, c | t1], [e, f | t2], [h, i | t3]], acc)
    end
  end

  def getsub([a, b, c | t], acc) when t == [] do
    check([a, b, c], acc)
  end

  def getsub([a, b, c | t], acc) do
    getsub([b, c | t], check([a, b, c], acc))
  end

  def run() do
    read("../data/day9.txt")
    |> getsub(0)
  end
end