Chess960 Initial Position Generator (Ruby)

chess960.rb

#!/usr/bin/ruby

board = Array.new(8)

# Bishops
2.times do |i|
  r = rand(4) * 2

  if i == 1
    r += 1
  end

  board[r] = "B"
end

# Queen, Knights
%w[Q N N].each do |s|
  empty = board.each_index.select { |i| board[i].nil? }
  board[empty.sample] = s
end

# Rook, King, Rook
%w[R K R].each do |s|
  board[board.index(nil)] = s
end

board.each do |i|
  print "#{i} "
end

puts