Google Software Engineering, Tools and Infrastructure, University Grad interview questions

I applied to Software Engineering, Tools and Infrastructure, University Grad position online on Oct 20, 2016. Received an email on Oct 27 for online coding assessment. Which had 2 coding questions (focused on string operations, they were bit difficult). I could not complete either of them, but still I was called for next round of phone interview. Which was almost 20 days later, requirement specified was really complex to understand at a go, but the interviewer made it simple by breaking down it into smaller pieces. I was able to solve them easily. It was exactly 45 min of interview. Apart from coding nothing else was asked. After 7 days I got rejection phone call.