Interviewing at Google Part 1

First let me state the obvious. It was a privilege working at Google for about 1.5 years. Mostly because of the quality of people you interact with and kind of computing infrastructure that you get to play around with. Even though I was not really overly excited by the actual projects I worked on yet it was a great leaning experience. But its not a complete utopia, there were many people there who felt they were not doing any great exciting work. This is primarily because Google is now a big company and no longer a startup and is growing at a tremendous rate. There are so many products that they have both customer facing and internal. So a large number of people will be working on adding some small feature in some product. That coupled with falling stock prices has definitely made Google a less lucrative prospect than before but as long as they manage to keep the enormously talented people they have, it will always be worth it working there.
One of the funs of working at Google was interviewing and I really looked forward to taking interviews. Most people start taking interviews pretty early just because there are large number of interviews happening and not too many interviewers. Google is seriously looking for people but not at the cost of quality, at least not yet. Here are some tips from my experience which I think people applying at Google will find useful. Ofcourse I will not divulge any actual question asked or anything about the internal review process of the interviews. But these are general tips which would be useful not just for Google but for other companies which have similar interviews like Amazon.
There are generally 4 types of questions that interviewers at Google ask.

1. Coding questions: Almost every interviewer will ask you to write code. Sometimes it might be a standalone question or it might be part of an Algorithm/System design question you were asked. The question usually will NOT require deep algorithms concept, rather it will be to test your clarity in thinking and ability to write Concise, Correct code that takes care of all the Corner Cases (IMPORTANT). Most of us believe that we are pretty good at coding, but in my short experience of interviewing at Google, I have hardly seen anyone write completely correct code in the first try. Maybe its the pressure of interview or maybe it is just lack of proper practice. So most important thing is to practice coding. And when I say coding, i don't mean pseudocode, I mean a proper, syntactically correct working code in any of your favorite language. Practice writing such code so that you do not make silly mistakes in interviews. Another reason why practice is important is that while coding in company, I hardly wrote code that involved things like tree traversal, dynamic programming, etc and I believe this to be true for most people. So practice in these basic areas:
a) Tree traversals
b) Dynamic Programming (Most Important)
c) Operations on Linked Lists such as merging, splitting etc.
d) Recursion
e) Even simple things like Sorting, Binary Search as one common mistake I have seen people make is losing track of correct array indices to pass in a Divide and Conquer type of code.

Once again do not just think about these things but practice. Practice writing nice elegant code but most importantly correct code. And also put all the proper error conditions check even while practicing. I am sure that this portion of the interview can be easily cracked if you have done enough homework. This is the easiest portion but also the easiest to make mistakes. Your code will be scrutinised very carefully by the interviewer and he will usually pick even a subtle mistake. So key word here is PRACTICE.