advent5.exs

defmodule Advent5 do
  def calculate_jumps(offsets, update_fn), do: calculate_jumps(offsets, 0, 0, update_fn)

  def calculate_jumps(_, count, current_index, _) when current_index < 0, do: count

  def calculate_jumps(offsets, count, current_index, update_fn) do
    if current_index > Enum.count(offsets) - 1 do
      count
    else
      current_offset = Enum.at(offsets, current_index)
      updated_offsets = List.update_at(offsets, current_index, update_fn)
      calculate_jumps(updated_offsets, count + 1, current_index + current_offset, update_fn)
    end
  end

  def increase_by_one(value), do: value + 1
  def strange_update(value) when value >= 3, do: value - 1
  def strange_update(value), do: value + 1
end

{:ok, input} = File.read("input5")

input
|> String.trim()
|> String.split("\n")
|> Enum.map(&String.to_integer/1)
|> Advent5.calculate_jumps(&Advent5.increase_by_one/1)
|> IO.inspect()

input
|> String.trim()
|> String.split("\n")
|> Enum.map(&String.to_integer/1)
|> Advent5.calculate_jumps(&Advent5.strange_update/1)
|> IO.inspect()