It probably doesn't matter too much unless the company is looking for proficiency in a particular language, and in that case you would know it going in to the i

It probably doesn't matter too much unless the company is looking for proficiency in a particular language, and in that case you would know it going in to the interview. When we give a coding problem, we let the candidate choose between C++ and C#, and the problems are such that the language doesn't really make much of a difference; other than minor IO and collections, there aren't any library calls. I prefer not having to explain why a reference to "cout" raises a compiler error (it's in a namespace), but the correctness of the algorithm is way more important.