I had two phone interviews with Google.

The first interview involved an algorithm to balance parentheses in a string, along with some design questions. I provided the solution, wrote the code, suggested improvements, and answered the design questions. The interviewer was very courteous and also showed that he respected my years of experience in the industry.

The second phone screen, however, was frustrating. The coding algorithm problem itself was not difficult; it was a substring extraction problem given a certain condition. You will find many examples of this on this website, and I have solved similar kinds of problems. Halfway through the problem, the interviewer started munching on an apple. I could clearly hear the crunching and chewing, and needless to say, it was distracting. I lost my train of thought and made a few mistakes. I knew before the call ended that I had to correct a number of things to make my code work. I guess I already knew the outcome of the call at that time.

What's disappointing is that I took a break and later attempted the problem myself, and I was able to do it in 20 minutes. It was a silly and frustrating thing to happen, and I feel disappointed that a good opportunity has been lost when the question is something I could have easily solved. I guess you do need luck.

Nothing difficult.