ABC088B - Card Game for Two

問題

https://atcoder.jp/contests/abs/tasks/abc088_b

回答2

defmodule Main do
  def main do
    :stdio
    |> IO.read(:all)
    |> solve()
    |> IO.puts()
  end

  defp split_lines(lines) do
    lines
    |> String.trim()
    |> String.split("\n")
  end

  defp split_words(words) do
    String.split(words, " ")
  end

  def solve(input) do
    input
    |> split_lines()
    |> Enum.at(1)
    |> split_words()
    |> Enum.map(&String.to_integer/1)
    |> Enum.sort(:desc)
    |> Enum.with_index()
    |> Enum.reduce(0, fn {num, index}, acc ->
      case rem(index, 2) do
        0 -> acc + num
        1 -> acc - num
      end
    end)
  end
end

"""
2
3 1
"""
|> Main.solve()
|> then(&(&1 == 2))

"""
3
2 7 4
"""
|> Main.solve()
|> then(&(&1 == 5))

"""
4
20 18 2 18
"""
|> Main.solve()
|> then(&(&1 == 18))