Ruby script to solve the puzzle in https://www.spotify.com/au/jobs/tech/reversed-binary/

binary_reverse.rb

class BinaryReverse
  def reverse(n)
    res = 0
    while n > 1 do
      res = res * 2 + n % 2
      n = n / 2
    end
    res * 2 + 1
  end
end

require 'test/unit'
class TestReverse < Test::Unit::TestCase
  def test_reserve_1
    obj = BinaryReverse.new
    output = obj.reverse 13
    assert_equal 11, output
  end

  def test_reserve_2
    obj = BinaryReverse.new
    output = obj.reverse 47
    assert_equal 61, output
  end
end