Google Software Engineer(Internship) interview questions

Got referral from a Google employee, finished an online code challenge, got email from recruiters to schedule 2 phone interviews. The interviewers called right on time, and asked to open the Google doc to code. The interviewer describe the question and gave examples, then ask you to think out loudly(meaning talk what you are thinking), then I proposed my solution, but the interviewer would ask you to increase the time or space efficiency. I didn't get enough time to write down my code.