Google Phone Interview

A couple of months ago, I got contacted from a recruiter working at Google. It was about a Software Engineer in Test position in Stockholm. I was a bit surprised because this position has been on the net for a long time and it was more than a year ago since I sent them my CV. Even though I am not pro-actively looking for a new job, you cannot say no if Google is asking. I replied back that I was interested and she called me back two days later. Google's recruiting process is very different compared to other companies I applied at. First there will be a one or more interviews over the telephone, and if you are good at those, you will be invited to an on-site interview. The on-site interview is a whole day where you will meet 5 to 7 interviewers each for a 45 min interview. Each interviewer will then write together an evaluation of your interview. All of the evaluations are reviewed by the hiring committee and if they decide to hire you, as one of the last steps, your documents including CV is sent over to the US headquarter for the final go or no-go.

So when the recruiter called me, this was actually the first step in a long recruiting process. The only thing she was interested during the fist call, was the length of my notice period and if it was negotiable. After this she asked me two technical questions. First question for the worst case time complexity of Quicksort. Second question something about Radixsort complexity, but she could not read the question, so she asked what the difference between a HashMap and a HashSet was. The recruiter is not really a technical person. She was probably given a list of questions and answers to filter out the very bad candidates. My answers were okay and she told me that she would set up a telephone interview.

A week or two passed. Since I did not hear from her, I wrote a mail asking for the status of the telephone interview. Due to vacations it took a bit longer to set up the interview. My recruiter told me that a confirmation would be sent soon. To prepare myself, I should be looking at the Google Testing blog. Also she wrote, that the interviewer would be interested in my testing background and that he would be asking questions relevant to my coding and problem solving skills, algorithms, core computer science concepts, OOP and datastructures. It could also be, that he asked me to write a test plan or how to test an arbitrary Google product like Maps or how I would design a cache. Also we would be talking about my projects, problems I had found, tested and fixed and also what I would do with my Google 20% time. It would also be good to know some stuff about the company, like the founders, the products, the business model etc.

The interview however, went completely different. Someone else sent me a confirmation mail including a link to a Google Docs document. which I could share with the interviewer. It was also suggested, that I "warm" up a bit on topcoder.com in the "Software Competitions - Algorithms" arena, which I did. On the day of my phone interview, I was called exactly at 11am. The interviewer was very friendly and explained everything very carefully.

For the first task I was given two Lists of Integers, one sorted ascending the other sorted descending. I should write an algorithm (Java) in the Google docs document, which would take both Lists and return a combined List that is sorted. I remembered that in the merge phase of the Mergesort, you do a similar thing. Have a pointer on the first element of the first list and a pointer on the last element in the second list. Then copy back the smaller of the two elements and increase or decrease the appropriate pointer.

The second task was about anagrams. Given a list of words, I was asked for a datastructure in which you could store anagrams. I suggested to use a Hashtable. Each word is effectively a character array that could be sorted. So sort the characters and use this as the key for the Hash function. That way, elements having the same key are anagrams of each other.

In the last task I was introduced to a Skip List, which I never heard of before. My interviewer explained the Skip List a couple of times and I was asked to write an algorithm for finding an element in the List. I did okay I think and then he asked me if I had any questions. I asked a bit about the Stockholm office, what he was working with at Google, if they used Git for version controlling (they use Perforce) and some other questions. I asked about feedback but he said, he is never giving feedback directly. Instead the interviewer said, he would write an evaluation of the interview in the next couple of days. Also he said, if later on I was asked to do another phone interview, it did not mean I was good or bad in the first one.

One week or so passed. My recruiter called me and said that they liked my interview and want to meet me for an on-site interview. Because Stockholm was not big enough and not so many test managers worked there, they would like to have the interview in Zürich. I would be given further details and date suggestions later on. Google pays the flight upfront. The hotel must be paid by the candidate but the money can be reimbursed by sending an expense form to Google in Poland. For those candidates staying overnight, Google also pays the food (30 Euro, US-Dollar or Pound depending on where the interview was held). Rental car fees can also be reimbursed. I decided to pay for everything myself, since I was not staying over night. Sending some reimbursement form to Poland, seemed complicated. I was given 4 days to choose from for the interview. I picked one but they set up the time on another day anyways - weird. So I was flying on-site to Google in Switzerland, roughly two months after the initial contact.