The interview process took about three weeks.

It started with an informal phone call with a recruiter, followed by a take-home coding test, and then two 45-minute phone interviews. After the second phone interview, I received an email stating that they would not be moving forward with me. I believe the next stage would have been an in-person interview loop.

The take-home coding test involved a Trinary Search Tree, as others have described. I think the main point of the exercise is to see how you handle duplicate entries, as the time complexity can be constant or linear depending on how you handle this case. I also wrote a bash script that ran several test cases on the Trinary Search Tree using input files and output the results to the terminal. There was a second question regarding converting a String to a Long, which has some tricky edge cases that must be accounted for, and I wrote a test script for that too.

The two 45-minute interviews were pretty standard. I don't remember the exact questions for the first, but they were basic coding tests done on CollabEdit. The first interviewer was helpful, and I answered the questions without much difficulty.

For the second 45-minute interview, I had an impatient interviewer who seemed ready to end the call as soon as possible. I initially paused while solving the Least Common Ancestor problem but managed to arrive at the optimal solution in about 15 minutes. However, at that point, we were about 25 minutes into the interview, and the interviewer decided he did not want to ask me a second question. I asked a couple of questions about Zillow, then the interviewer ended the call early (about 35 minutes in).

The interview process was positive up until the last interviewer, who came across as a busy engineer that wanted to end the call before it began. I feel as though with a less hurried interviewer, I may have moved on to an interview loop.

Having spent a considerable amount of time preparing for the interviews, doing the take-home coding tests, and going through the actual interviews, I feel that the least the interviewer could have done was to ask the second coding question and finish out the interview.

I would not seek out an interview with Zillow again based on my experience.

Protip: I believe all the questions I received are ones that are already posted on Glassdoor. Already knowing the optimal solutions to those questions should help immensely for anyone interviewing in the future.

Find the Least Common Ancestor given two nodes of a binary tree.

The nodes each have a reference to their parent node, and you do not have the root node of the tree.