Day 7: The Treachery of Whales

Setup

Mix.install([
  {:kino, "~> 0.4.1"}
])

Input

input = Kino.Input.textarea("Input")

Part 1

defmodule M do
  def fuel_cost(positions, pos) do
    positions
    |> Enum.map(&abs(&1 - pos))
    |> Enum.sum()
  end
end

Kino.Input.read(input)
|> String.split(",")
|> Enum.map(&String.to_integer(&1))
|> then(&Enum.map(Enum.min(&1)..Enum.max(&1), fn p -> M.fuel_cost(&1, p) end))
|> Enum.min()

Part 2

defmodule M do
  def fuel_cost(positions, pos) do
    positions
    |> Enum.map(fn p ->
      x = abs(p - pos)
      (x + 1) * x / 2
    end)
    |> Enum.sum()
  end
end

Kino.Input.read(input)
|> String.split(",")
|> Enum.map(&String.to_integer(&1))
|> then(&Enum.map(Enum.min(&1)..Enum.max(&1), fn p -> M.fuel_cost(&1, p) end))
|> Enum.min()