Google Telephonic Interview

So finally my interview for google recruitment process was scheduled on 22 january 11.30 pm IST by antara pathak HR frm Google ,India. I was scheduled to speak with Nirnimesh an engineer in Google USA.
Since signal strength was very low in my room I was ready with pen ,paper and ofcourse laptop in my friend Neeraj's room. I was waiting for his call in his room. Finally he called me at 11.45 pm IST ,15 minutes late from scheduled time . First of all he asked me to prepare with everything for this interview ,so he gave me 5 more minutes.
He started with my current final year project which i am doing.I told him about my project on Content based image retrieval ,its current status and my future work.He asked many tricky questions from this project.He then moved onto my summer project 'FILE SYSTEM' .It was mentioned in my resume which was given to him. Actually I had implemented the file system which was limited to main memory of computer.He asked me " why are you calling this file system". He then asked me to think to remove this limitation from file system.I told him my approach. He then told some features which could be implemented.

Finally He asked one coding question.I was asked to write a code for function which takes pointer to the root of a Binary tree not BST and return value of that element which occurs maximum number of times. Initially I gave him the solution which was of O(n^2) complexity.He asked me to optimise my algorithm.Finally I came with solution which was of (n) but space complexity got worse in this case. Finally he said he was running out of time and asked me if i had any questions to ask. I asked him to rate my interview. Also I asked him how to improve coding skills .He told me take part in topcoder competetions and other online coding contest.
He told me that Google India is an exact copy of Google USA and told that he would like to meet me in India if am selected for an offer.With this happy note my interview was winded .He grilled me at many occasions but I would say it was a great experience.