Before an interview they gave me an assignment to write an application in C++ that generates and sorts strings in a file. The challenge was that the file size should be very large - 10 Gb. I liked the challenge and spent a weekend working on it, trying and evaluating different sorting algorithms to make it work faster. The interview process was less exciting though. They did not even say thank you for writing the assignment or congratulate me with passing the first stage, but started from attacking my writing style. They did not give me any guidelines about writing style, etc. so their complains took me by surprise. They spent half an hour asking me why I did not use a smart pointer and simply used a pointer in some part. That's such a waste of time and made an impression that they did not prepare for an interview.