Day 7

input =
  File.read!("day7.txt")
  |> String.trim()
  |> String.split(",")
  |> Enum.map(&String.to_integer/1)

[1101, 1, 29, 67, 1102, 0, 1, 65, 1008, 65, 35, 66, 1005, 66, 28, 1, 67, 65, 20, 4, 0, 1001, 65, 1,
 65, 1106, 0, 8, 99, 35, 67, 101, 99, 105, 32, 110, 39, 101, 115, 116, 32, 112, 97, 115, 32, 117,
 110, 101, 32, 105, ...]

Task 1

median = Enum.at(Enum.sort(input), div(length(input), 2))

input
|> Enum.map(&abs(&1 - median))
|> Enum.sum()

336721

Task 2

arith_sum = fn n -> div(n * n + n, 2) end

max = Enum.max(input)

mean = Enum.sum(input) / length(input)

[floor(mean), ceil(mean)]
|> Enum.map(fn n ->
  input
  |> Enum.map(&arith_sum.(abs(&1 - n)))
  |> Enum.sum()
end)
|> Enum.min()

91638945