Day2

Mix.install([
  {:kino_aoc, git: "https://github.com/ljgago/kino_aoc"}
])

Setup

{:ok, data} = KinoAOC.download_puzzle("2024", "2", System.fetch_env!("LB_AOC_SECRET"))

Solve

defmodule Day2 do
  def parse(data) do
    data
    |> String.split("\n", trim: true)
    |> Enum.map(fn r -> r |> String.split() |> Enum.map(&String.to_integer/1) end)
  end

  def solve(data) do
    dd = parse(data)
    task1(dd) |> IO.inspect(label: "res 1")
    task2(dd) |> IO.inspect(label: "res 2")
  end

  def check(row) do
    cr = Enum.chunk_every(row, 2, 1, :discard)
    Enum.all?(cr, fn [a, b] -> a >= b && d3(a,b) end) ||
    Enum.all?(cr, fn [a, b] -> a <= b &amp;&amp; d3(a,b) end)
  end

  def d3(a, b) do
    d3 = abs(a - b)
    d3 <=3 &amp;&amp; d3 >= 1
  end

  def task1(data) do
    Enum.count(data, fn row -> check(row) end)
  end

  def task2(data) do
    data
    |> Enum.count(fn row ->
      0..length(row)-1
      |> Enum.any?(fn i ->
        nr = List.delete_at(row, i)
        check(nr)
      end)
    end)
  end

  def permutations(row) do
    0..length(row)-1
  end
end

tdata =
"""
7 6 4 2 1
1 2 7 8 9
9 7 6 2 1
1 3 2 4 5
8 6 4 4 1
1 3 6 7 9
"""

Day2.solve(tdata)
Day2.solve(data)