Kuaishou Intern Interview

Posted on Edited on In Disqus:

Thanks to senior schoolmate @lxc for the referral and interview advice, I was fortunate enough to attend the interview for an algorithm intern role in Kuaishou’s recommendation group, and I eventually passed the interview and received the offer.
Although intern interviews may be relatively simple, I think this still has reference value.
Doing internships can be considered one route toward eventually finding a good job and joining a dream company. It cannot really be called a shortcut; the two internships I did were both quite tiring. Kuaishou was my second internship.
Now that the internship has finally stabilized, and there is still some time before the deadline for my graduation thesis, I happen to have time to summarize my interview and internship.
I hope this can guide my future search for other internships or full-time jobs :)

Interview

I went through two rounds of interviews in total, taking nearly two hours.
Overall, I felt that my preparation was not sufficient, and many areas still needed improvement.

First Round

The interviewer was a friendly, slightly chubby engineer. He was very kind and took the interview seriously.
After I started the internship, I often ran into him during meetings and meals, which felt very familiar. We were not in the same team, but we were in the same larger group.

Interview content:

  • Given an array, find the contiguous subsequence with the maximum sum and return the sum;
  • Reverse a sentence: for example, today is wednesday! => wednesday is today!
  • SQL-related: differences between left join, right join, and inner join; whether I knew partition;
  • Machine learning-related: definitions of precision and recall.

Second Round

The interviewer was a serious engineer. My impression was that he reacted very quickly, possibly someone at the leader level.
Unfortunately, after joining I never saw him in the larger group.

  • When memory is extremely small, find the position of number m among a large number of values.
  • When a = b, where might b be obtained from? Register, cache, memory, external storage.
  • Given a sorted array cyclically shifted left by an unknown k, find the position of number m.
  • There are n stairs, and you can walk 1 step or 2 steps… He first asked whether I had done this problem before. I said yes, so he did not ask me to do it again.
  • Given a binary tree where each node stores a number, find the lowest common ancestor of two numbers.
  • Differences between multi-process and multi-threading;
  • Use of inter-process communication in Java and C++;
  • Use of socket libraries for network communication in Java and C++. (I did not answer these two well.)
  • My level of understanding of machine learning, and whether I had studied loss functions.

Interview Preparation

After this interview, I became clearer about what to prepare for interviews:

  • Data structures and algorithms are the foundation, and must be reviewed and practiced carefully.
  • SQL, machine learning, and Hadoop are bonus skills.
  • Handwritten code and short-answer questions are the main content of interviews.

In fact, I answered the SQL, machine learning, and multi-threading questions very poorly. Only the algorithm problems were answered passably; I did write them all out, although there were some mistakes in the middle and they may have taken a long time, especially the first handwritten problem, where I had not yet entered the right state and spent extra time.

Based on my senior schoolmate’s advice, I think the following preparation path and resources are relatively efficient, and I am still preparing:

  • Data structures and algorithms: COS226 + Algorithms, 4th Edition, Elements of Programming Interviews
  • SQL: Sams Teach Yourself SQL in 10 Minutes, runoob
  • Multi-threading: Java Concurrency in Practice
  • Machine learning: Zhou Zhihua’s Machine Learning, also known as the “Watermelon Book”

Onboarding

Earlier, because of my graduation thesis, I hesitated over whether to accept the internship offer.
After consulting my senior schoolmate and weighing the pros and cons, I finally accepted the offer and joined on April 19.
The offer package was: 300 per day, lunch, afternoon tea, and dinner covered, with fruit, milk, and ice cream available freely.
In reality:
300 per day before tax. Interns are taxed as service income, and the portion above 800 is taxed by the state at 20%.
Lunch and dinner are still great, especially the lunch buffet; I overeat every time.
Afternoon tea is simple: a kraft paper bag with drinks, fruit, and snacks. It differs from what I imagined, but is still quite satisfying; I often leave some and take it back to eat.

From the little details at work, I can feel that
Kuaishou is a company with strong technology and many excellent people. It is now expanding rapidly; almost every week someone joins our group (is that why I was admitted?).
The two mentors guiding me are also very nice. I have learned and grown a lot from work.