I think this is cute but I would think hard about the kinds of questions you develop for this. Coming from the perspective of someone working for a big company with a ton of software people that is not a tech company, I could use something like this in general. But, the question you asked is the kind of thing I ask CS undergrads (almost exactly, in fact) because it allows for clever solutions without actually requiring someone to be a particularly good programmer. I can work through it with them and if the basic solution is easy, prompt them to give me something more clever, so I know how they think, which is good when you're looking at an inexperienced developer. However, for an experienced developer that I want to hire to churn out Java code, the difference to me between a correct but simple O(n^2) solution vs a clever O(n) is not terribly meaningful for determining whether they can actually do what I want them to do. I want something that requires people to write more than a handful of lines and demonstrates an ability to keep track of a few more variables correctly, and honestly I don't care all that much about their algorithmic complexity (although I might care a great deal about their space usage, usage of external resources, etc). So, if this is the audience you are looking to attract, consider thinking about this as a screening tool for people outside of the startup world that actually need "knows how to really do shit in language X" more than "knows how to write clever algorithm,"