diamond.rb

end_char = ARGV.first

characters = ('A'..end_char).to_a + ('A'...end_char).to_a.reverse
max_level = end_char.ord - 'A'.ord

diamond = characters.map do |char|
  current_level = char.ord - 'A'.ord
  before_spaces = max_level - current_level

  if char == 'A'
    ' ' * before_spaces + char
  else
    inner_spaces = (current_level - 1) * 2 + 1
    ' ' * before_spaces + char + ' ' * inner_spaces + char
  end
end.join("\n")

puts diamond