reversi

reversi.rb

class Board
  def initialize(size = 8)
    @size = size
    @board = []
    @size.times do
      row = []
      @size.times { row << :none }
      @board << row
    end

    c = @size / 2
    @board[c - 1][c - 1] = :black
    @board[c][c] = :black
    @board[c - 1][c] = :white
    @board[c][c - 1] = :white
  end

  def place(color, x, y)
    return [0, 'out of bounds'] if x < 0 || y < 0 || x >= @size || y >= @size
    return [0, 'occupied'] if @board[y][x] != :none

    opposite_color = color == :black ? :white : :black
    total_reversed = 0

    [[-1, -1], [-1, 0], [-1, 1], [0, -1], [0, 1], [1, -1], [1, 0], [1, 1]].each do |dy, dx|
      nx = x + dx
      ny = y + dy

      count = 0

      while nx >= 0 && ny >= 0 && nx < @size && ny < @size && @board[ny][nx] == opposite_color
        nx += dx
        ny += dy
        count += 1
      end

      next if count == 0
      next unless @board[ny][nx] == color

      total_reversed += count

      rdx = -1 * dx
      rdy = -1 * dy

      while nx != x || ny != y
        @board[ny][nx] = color
        nx += rdx
        ny += rdy
      end
    end

    if total_reversed == 0
      return [0, 'cannot reverse anything']
    end

    @board[y][x] = color
    [total_reversed, 'ok']
  end

  def show
    puts " |#{(0..(@size - 1)).to_a.join('|')}|"
    @size.times do |y|
      row = @board[y].map { |cell| cell_to_char(cell) }.join('|')
      puts "#{y}|#{row}|"
    end
    puts '-' * 17
  end

  private

  def cell_to_char(cell)
    case cell
    when :none then ' '
    when :black then '*'
    when :white then 'o'
    end
  end
end

board = Board.new
board.show
turn = :black

puts turn

while (str = gets)
  x, y = str.chomp.split.map(&:to_i)

  reversed, msg = board.place(turn, x, y)
  if reversed > 0
    turn = turn == :black ? :white : :black
    board.show
  else
    puts msg
  end

  puts turn
end

振り返り中に fail じゃなくてエラーメッセージを表示するようにしました