I found the interview to be smooth, and everyone was really friendly. It was a great experience.

Someone in the company referred me, and then I applied online. I applied in September, and the process took four weeks before I could arrange a phone interview.

Phone Interview: The phone interview was easy, with no C++ questions. First, I introduced myself and answered some behavioral questions. Then, a technical question: given a sorted array, how do you check if all the numbers are prime numbers? The array is sorted, and you just need to return true or false. I then wrote the code, followed by many follow-up questions for this problem.

I received an offer for the onsite interview the next day.

Onsite Interview: The onsite interview was on October 28th. Business professional attire was required, and I wore it. Strangely, none of the interviewers wore suits, but they asked all interviewees to do so. We first took a tour around the company, seeing the famous curved elevator, the fish tank, and the sky view on the 29th floor. Nothing was particularly special. Then, we went to another part of the building for the interviews.

1st Round: This round was with a white interviewer and an Indian interviewer. They first introduced themselves and then asked me to talk about myself. The technical problem was: given a binary tree, how to output it level by level. I initially thought about saving it in a structure, which would take space, so I then considered an iterative method to traverse the tree using two queues or calculating the length for one level. The next question was: given a string with spaces removed, how could you recover the original one? I got stuck not because it was too hard, but because I didn't understand what kind of solution they wanted. Finally, the interviewer explained it himself: use an encoding method to encode all the original text, which could represent all different characters.

2nd Round: This round was with two traditional Americans who worked on the same team. They had just arrived. First, some behavioral questions. The first technical question was: given an array of integers, how do you find the first unique element? My first thought was a naive approach: scan from the first element, and if there's a duplicate, move to the next. The second method was more straightforward: use a hash map to store all elements and their counts. If there's a duplicate, increment the count.

The next question was about how to deal with a random music player. We started with the shuffle algorithm and then discussed using an array to handle random and non-repeating elements.

3rd Round: This was with a manager from the help team. We talked about my background and then some behavioral questions.

Brain Teaser: Given 3-liter and 7-liter buckets, how to get 4 liters of water? Follow-up: Given 4-minute and 7-minute hourglasses, how to get 9 minutes?

4th Round: This was an HR interview, a lot of general conversation.

The whole interview process was quite pleasant, except for the difficult encoding question. The visit was nice, and the office looked great. Anyway, it was good to get an offer early! (I heard back from HR two days after the interview.)

A function accepts string input. The output would delete all the spaces. How could you recover the original one?