[Shenglong]

With the exception of the last part of the question, you learn everything there in your first year of CS at university. Do people who can't write this really put the language on their resume?

Can I get some stats? I really don't (want to) believe it. What percentage of people get this question wrong? Are they all some sort of eng/cs graduate? I'm not even a coder and I can solve this in a few minutes.

[dtunkelang]

I don't have stats I can share, but I assure you that this problem has confounded many interview candidates with strong resumes. I agree with you that it's all basic material -- that's deliberate. I'm glad you think it's too easy. :-)

[cema]

Yes, it's basic. But many people who are not fresh out of college may have spent recent years solving a completely different set of programming tasks, and do not have it loaded in their brains.

When applicants prepare for an interview, they do not often know what kind of knowledge to load in their heads. For example, just a couple of weeks ago I was asked to figure out a simple bit-flipping scheme, and bit string manipulations are something that I have not thought about in many years. So it took me about 10 minutes for a problem that I would have done in less than a minute when I was spending time thinking about similar things and my mind was full with them.

Being prepared for a technical interview does not mean to have memorized a few solutions to a few problems, but it means to have played with them sufficiently to have the brain loaded with the material. This helps with intuition as well as specific technical skills.

[Shenglong]

You have my sympathy :)