def rot13(secret_messages)
  secret_messages.collect{|value| 
    value.bytes.each_index{|index|
      code = value.getbyte(index)
      value.setbyte(index, (code+13)) if( code > 64 && code < 78 || code > 96 && code < 110)
      value.setbyte(index, (code-13)) if( code > 77 && code < 91 || code > 109 && code < 123)
    }
  }
  secret_messages
end

def rot13(secret_messages)
    secret_messages.map {
        |msg| decipher_message(msg)
    }
end

def decipher_message(msg)
    msg.chars.map { |c|
        case c
            when 'a'..'m', 'A'..'M'
                (c.ord + 13).chr
            when 'n'..'z', 'N'..'Z'
                (c.ord - 13).chr
            else
                c
        end
    }.join
end

def rot13(secret_messages)
   secret_messages.map do |word|
     word.tr("a-z", "n-za-m")
   end
 end

def rot13(secret_messages)
    secret_messages.map do |str|
        str.chars.map{|char| char.ord.between?(65,90) || char.ord.between?(97,122) ? cipher(char) : char }.join
    end
end

def cipher(char)
    13.times {char.next!}
    return char.size > 1 ? char[1] : char
end