Senior developer interview questions shared by candidates
You have 20 minutes to a write a syntactically correct program in C# that will create all the possible letter/word combinations of a telephone key pad for a 7 digit number. You are not allowed to use a pen and paper. You are not allowed to use Visual Studio, but an editor we provide, however it must work correctly when we run it in Visual Studio. Both interviewers watching me and making notes. Interview question was not prepared but hastily typed up by tech lead who had a poor grasp of written English, I had to help him correct his question several times. The editor they gave me was poor and had its own learning curve which I doubt they scoped in. A decent question ruined by ill thought and pointless caveats.
An almost impossible task given the circumstances which I did not complete and which they allowed to go over the 20 mins. I kept mentioning a recursive solution to them and one interviewer (lets call him 'M') in particular kept huffing and rolling his eyes every time I mentioned recursion. Interview was cut by M who had the audacity to tell me that a recursive solution is wrong. 'M' then admitted he had not sat test under same conditions. I asked both interviewers for the answer they were looking for, but they actually refused to give it to me and 'M' told me to go and Google it ! So it transpired that 'M' was quite happy to tell me I was wrong, and that he thought he could do the test under the same conditions, but could not back up his claims with his own solution. Farce really. Neither interviewer went through my CV, showed any interest in me or told me about Trayport. Shambolic. As a veteran of many interviews I have never been treated so badly. I got home and wrote my own solution using recursion which I sent to Trayport's HR manager to pass on. I also googled the solution as M said, would you believe it, first three solutions I came across used recursion. Go figure. There are many ways to solve this problem and a Tech Lead should be open to all.
A simple permutation question that should take 5 minutes to develop, solution: http://stackoverflow.com/q/1851239. The editor was http://collabedit.com/ which is what e.g. Facebook uses. The reason I huffed and puffed is because the candidate kept getting lost and complaining about minutiae instead of showing technical skills.
M's linked answer uses recursion. Trayport sound like a nightmare.