Advent of Code - Day 2

Mix.install([
  {:req, "~> 0.5.8"}
])

Input

opts = [headers: [{"cookie", "session=#{System.fetch_env!("AOC_SESSION_COOKIE")}"}]]
input = Req.get!("https://adventofcode.com/2024/day/2/input", opts).body

Part 1

defmodule Aoc2024.Day2 do

  # opts = [headers: [{"cookie", "session=#{System.fetch_env!("AOC_SESSION_COOKIE")}"}]]
  # input = Req.get!("https://adventofcode.com/2024/day/2/input", opts).body

  def part_1(input) do
    input 
      |> String.split("\n", trim: true)
      |> Enum.map(&convert_to_int_list/1)
      |> Enum.map(&check_report/1)
      |> Enum.count(fn s -> elem(s, 0) == :safe end)     
  end

  def part_2(input) do
    input 
      |> String.split("\n", trim: true)
      |> Enum.map(&convert_to_int_list/1)
      |> Enum.map(&is_safe_combinations?/1)
      |> Enum.count(fn s -> s == true end)
  end

  defp convert_to_int_list(readings) do
    readings
    |> String.split()
    |> Enum.map(&String.to_integer/1)    
  end

  defp is_safe_combinations?(reading) do
    [reading | (for idx <- (0..length(reading) - 1), do: List.delete_at(reading, idx))]
    |> Enum.map(&amp;check_report/1)
    |> Enum.any?(fn s -> elem(s, 0) == :safe end)
  end

  defp check_report(reading) do
    reading
    |> Enum.reduce({:unknown}, fn x, acc -> 
      case acc do
        {:unsafe} -> 
          {:unsafe}
        {:unknown} -> 
          {:safe, :unknown, x}
        {:safe, :unknown, prev} when prev < x and abs(prev - x) < 4  ->
          {:safe, :increasing, x}
        {:safe, :unknown, prev} when prev > x and abs(prev - x) < 4 ->
          {:safe, :decreasing, x}
        {:safe, :increasing, prev} when prev < x and abs(prev - x) < 4 ->
          {:safe, :increasing, x}
        {:safe, :decreasing, prev} when prev > x and abs(prev - x) < 4 ->
          {:safe, :decreasing, x}
        _ ->
          {:unsafe}            
      end    
      end)
  end
  
end

#test = 
#  "7 6 4 2 1"
#  |> String.split("\n", trim: true)
#  |> Enum.map(&Aoc2024.Day2.convert_to_int_list/1)

#[reading | _] = test

#for idx <- (0..length(reading) - 1), do: List.delete_at(reading, idx)

#reading = [14, 17, 20, 21, 24, 26, 27, 24]
#combos = [reading | (for idx <- (0..length(reading) - 1), do: List.delete_at(reading, idx))]
#IO.inspect(combos)




#Aoc2024.Day2.part_1(input)

#reading = [14, 17, 20, 21, 24, 26, 27, 24]
#Aoc2024.Day2.is_safe_combinations?(reading)

Aoc2024.Day2.part_2(input)

#