Day 1

Mix.install([:kino])

Read Input

file_input = Kino.Input.file("Select Input File")

file_value = Kino.Input.read(file_input)
file_path = Kino.Input.file_path(file_value.file_ref)
contents = File.read!(file_path)

Part 1

sum = contents
  |> String.split("\n")
  |> Enum.reject(fn line -> String.length(String.trim(line)) == 0 end)
  |> Enum.map(fn line -> 
    ~r/(\d+)\s*(\d+)/
    |> Regex.run(line)
    |> Enum.slice(1..2)
    |> Enum.map(&String.to_integer/1)
    |> then(fn [first, second] -> {first, second} end)
  end)
  |> Enum.unzip()
  |> then(fn {a, b} -> Enum.zip(Enum.sort(a), Enum.sort(b)) end)
  |> Enum.reduce(0, fn ({a, b}, sum) -> sum + abs(a - b) end)

Part 2

sum = contents
  |> String.split("\n")
  |> Enum.reject(fn line -> String.length(String.trim(line)) == 0 end)
  |> Enum.map(fn line -> 
    ~r/(\d+)\s*(\d+)/
    |> Regex.run(line)
    |> Enum.slice(1..2)
    |> Enum.map(&String.to_integer/1)
    |> then(fn [first, second] -> {first, second} end)
  end)
  |> Enum.unzip()
  |> then(fn {a, b} -> 
    frequencies = Enum.frequencies(b) 
    Enum.reduce(a, 0, fn(i, sum) ->
      sum + i * Map.get(frequencies, i, 0)
    end)
  end)