Google Software Development Engineer interview questions

Google invited me to onsite interview. The recruiting team booked hotel and flight for me. The process is professional. There are four rounds with a lunch break in the middle. The interviewers are friendly. For each round, I was supposed to solve an algorithm problem on a white board. Those problems are not easy.

It was a technique phone interview. The task was not very hard, but I didn't prepare very well at that time. HR is very nice and could reply to question in time.