Day 1: Historian Hysteria

Mix.install([:kino])

Section

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

input = Kino.Input.read(input) |> String.split("\n", trim: true)

Part 1

lists = Enum.reduce(input, %{left: [], right: []}, fn (item, %{left: left, right: right}) -> 
  [l, r] = String.split(item, " ", trim: true) |> Enum.map(&(String.to_integer(&1)))
  %{left: [l | left], right: [r | right]}
end)

Enum.zip([Enum.sort(lists.left), Enum.sort(lists.right)]) |> 
Enum.map(fn 
  {l, r} when r > l -> r - l
  {l, r} when r <= l -> l - r
end) |> 
Enum.sum()

Part 2

%{left: left, right: right} = Enum.reduce(input, %{left: [], right: []}, fn (item, %{left: left, right: right}) -> 
  [l, r] = String.split(item, " ", trim: true) |> Enum.map(&(String.to_integer(&1)))
  %{left: [l | left], right: [r | right]}
end)

Enum.reduce(left, 0, fn (left_item, acc) -> 
  acc + Enum.count(right, fn i -> left_item == i end) * left_item
end)