to_binary.rb

def to_binary(number)
  returning = []

  if number.odd?
    returning << 1
    number -= 1
  end

  while number > 0
    i = 1
    while 2 ** i <= number
      if 2 ** (i + 1) > number
        returning[i] = 1
        number -= (2 ** i)
        break
      end
      i += 1
    end
  end
  returning.map{|num| num.nil? ? "0" : "#{num}"}.reverse.join.to_i
end