Note I'm not saying to do interviews in Python and ruby but if you're solid in one of them it's like real working pseudocode compared to Java c# c++. But use your a#1 solidest language. Unless u have more than one and that language makes a particular problem trivial.
I am most comfy with Python but think it is the wrong language for me to do coding interviews. When I was in school, I was taught intro CS in C and Java. I got tripped by a fairly CS 101 question even though I use Python very productively and regularly at work. In C or Java, I'd be able to knock off that question easily.
As I said, it depends. If it's text heavy, python or ruby (or perl) is likely the best. If it uses a lesser known data structure, maybe java with it's massive set of libraries. If it's bit twiddling or memory intensive, then maybe c++ is the right answer. But a lot of questions are trivial in ruby or python. 3sum can be done in 2 lines of ruby (how I wish it was one, would be cooler).
