소개

Elixir 즐기십니까

준비

잘못하면

mix new

$ mix new rails_on_tiles
$ cd rails_on_tiles

소스 코드 작성

defmodule RailsOnTiles do
  @moduledoc """
  Documentation for `RailsOnTiles`.
  """

  @tiles [[2, 3, 0, 1], [1, 0, 3, 2], [3, 2, 1, 0]]
  @dirs [[0, -1], [1, 0], [0, 1], [-1, 0]]
  @alphabets ?A..?I

  @doc """
  Rails on Tiles（どう書く）

  ## Examples
  iex> RailsOnTiles.go("101221102")
  "BEDGHIFEH"

  iex> RailsOnTiles.go("000000000")
  "BEH"

  iex> RailsOnTiles.go("111111111")
  "BCF"

  iex> RailsOnTiles.go("222222222")
  "BAD"

  iex> RailsOnTiles.go("000211112")
  "BEFIHEDGH"

  iex> RailsOnTiles.go("221011102")
  "BADGHIFEBCF"

  iex> RailsOnTiles.go("201100112")
  "BEHIFCBADEF"

  iex> RailsOnTiles.go("000111222")
  "BEFIH"

  iex> RailsOnTiles.go("012012012")
  "BC"

  iex> RailsOnTiles.go("201120111")
  "BEDABCFI"

  iex> RailsOnTiles.go("220111122")
  "BADEHGD"

  iex> RailsOnTiles.go("221011022")
  "BADG"

  iex> RailsOnTiles.go("111000112")
  "BCFIHEBA"

  iex> RailsOnTiles.go("001211001")
  "BEFI"

  iex> RailsOnTiles.go("111222012")
  "BCFEHIF"

  iex> RailsOnTiles.go("220111211")
  "BADEHI"

  iex> RailsOnTiles.go("211212212")
  "BCFEBAD"

  iex> RailsOnTiles.go("002112210")
  "BEFC"

  iex> RailsOnTiles.go("001010221")
  "BEF"

  iex> RailsOnTiles.go("100211002")
  "BEFIHG"

  iex> RailsOnTiles.go("201212121")
  "BEFCBAD"
  """
  def go(input) do
    String.codepoints(input)
    |> Enum.map(&String.to_integer/1)
    |> Enum.chunk_every(3)
    |> solve()
    |> Enum.map(&Enum.at(@alphabets, &1))
    |> Enum.map(&<<&1>>)
    |> Enum.join()
  end

  defp solve(field) do
    {x, y} = new_xy(1, -1, 2)
    do_solve(field, x, y, 2, [])
  end

  defp do_solve(_field, x, y, _dir, route) when x < 0 or x > 2 or y < 0 or y > 2, do: route

  defp do_solve(field, x, y, dir, route) do
    rev = get_in(@tiles, [Access.at(0), Access.at(dir)])

    nxt =
      get_in(@tiles, [
        get_in(field, [Access.at(y), Access.at(x)]) |> Access.at(),
        Access.at(rev)
      ])

    tile_num = y * 3 + x

    {x, y} = new_xy(x, y, nxt)
    do_solve(field, x, y, nxt, route ++ [tile_num])
  end

  defp new_xy(x, y, dir) do
    [dx, dy] = Enum.at(@dirs, dir)
    x = x + dx
    y = y + dy

    {x, y}
  end
end

Doctests

## Examples 아래에있는 것은 Doctests이라는 것으로 테스트 할 수 있습니다

$ mix test
......................

Finished in 0.08 seconds
21 doctests, 1 test, 0 failures

Wrapping Up 🎍🎍🎍🎍🎍

문제를 해결하는 방법을 전혀 알지 못했습니다.

Enjoy Elixir