Google Software Development Engineer I interview questions

The whole process took me about a month. At first I sent my CV and cover letter (it is very important to send good cover letters). Then I was contacted by a recruiter within 2 days. He told me about an interview process, gave me some materials for interview preparation. The first interview I had was hangouts interview with an engineer. I did well with my first task: at first, I made bad and simple solution and then tried to improve its time and memory complexity. After that I had a question about some class interface design. And after that I were waiting for about 3 weeks to get a negative decision, because my first solution was too simple. As I think my interviewer just forgot about me and wrote something, so I didn't pass.

Got the interview through employee referral. Contacted by HR over one month after the submission of referral. Two rounds of phone interviews on the same day. Both are coding questions.