2021-08-06

Summary of My Postgraduate Recommendation Summer Camps

I document my experience of the postgraduate recommendation summer camps here for reference for younger schoolmates. The main experiences are as follows:

  • I planned to visit Shenzhen, but due to the COVID-19 outbreak there, the SUSTech summer camp was switched online.
  • I planned to visit Nanjing, but due to the COVID-19 outbreak there, the NJU summer camp was also switched online.
  • Finally, only my home university remained offline, but then Xiamen had an outbreak, and the city became medium-risk after the holiday.

1. School Selection Criteria

Before applying, I first clarified my school selection criteria. My standards are listed below, not very different from those I used for college applications three years ago:

  1. Computer science strength ≥ XMU; supervisors with solid reputations in networking or cybersecurity are preferred; only academic master’s programs are considered.
  2. Pleasant climate, not extremely cold in winter, and good air quality. Therefore, schools north of the Yangtze River and non‑coastal provinces are excluded.
  3. Moderately sized city with nice scenery and friendly locals. Therefore, cities similar to Xiamen are preferred; cold and exclusive cities like Beijing and Shanghai are excluded.
  4. Balanced gender ratio and a certain humanistic atmosphere. Therefore, comprehensive universities are prioritized; purely science & engineering, tech‑focused universities and research institutes are excluded.
  5. Good campus environment, accommodation and dining, convenient access to downtown. Therefore, campuses near the city center or with direct metro access are preferred; remote and inconvenient campuses such as XMU Xiang’an Campus are excluded.

Therefore, before our college moved to Xiang’an, my home university was always the best choice. Besides my home university, few schools meet all these conditions. In the order of priority 1–5 above, the schools that best fit are:

  1. Zhejiang University, Nanjing University
  2. Xiamen University (home), Fudan University, Sun Yat‑sen University
  3. Southern University of Science and Technology, Shanghai Jiao Tong University

I thus applied for summer camps at the above schools. Since ZJU’s Computer Science only offered direct PhD programs, I applied to the School of Software. For Fudan, I applied for Cyberspace Security.

2. Application and Admission

Required application materials were mostly consistent: resume, academic transcript, ranking certificate, CET‑4/6 report, copies of student ID and national ID, award certificates, etc. Only my home university and SUSTech required the application form stamped by the college; NJU required stamping only after admission was confirmed.

In addition, only my home university mandatory required two recommendation letters from associate professors or above (was all this bureaucracy really necessary?). SUSTech had optional recommendation letters: one from a counselor, one from a course instructor. All other schools did not require recommendation letters.

Notably: For stamped electronic PDFs, it is better to print, scan or export them as images. Otherwise, the stamp can be directly selected and edited with PDF editors, which undermines authenticity. I almost missed the admission because of this issue!

I was rejected directly by Fudan University and Shanghai Jiao Tong University due to ranking (I was exactly at 10%, and the cutoff was likely around 5%). NJU passed the initial material review, but due to the large number of applicants, an online written test was required for further screening (I later learned the cutoff was exactly 10%, quite lucky). All other schools admitted me directly.

After admission, with the help of classmates, I learned about the reputations of some schools. I found that ZJU’s School of Software graduate students were based in Ningbo; its A+ in Software Engineering actually belonged to the School of Computer Science, with weak faculty, and it was just a resume‑polishing place. Sun Yat‑sen University had serious bureaucracy, which was reflected in the tone of teachers in the summer camp group, and it was only slightly better than XMU. I thus gave up the admission to these two schools.

Now only three summer camps remained:

  • July 5: SUSTech online interview
  • July 8: NJU online written test screening
  • July 10–11: Home university offline written test + programming test + interview

3. Southern University of Science and Technology (SUSTech)

Although SUSTech does not have many titles, its computer science faculty is outstanding, much stronger than my home university. Originally planned as an offline summer camp, it was switched online due to the COVID‑19 outbreak in Guangzhou and Shenzhen, with a single 30‑minute interview.

There were about 4 teachers, most with cameras off. First, a 1‑minute English self‑introduction. Then I drew one question each from humanities literacy, professional literacy, and research potential. My questions and answers:

  1. What do you think a successful life is? How do you define personal success? > Do what you want to do.

  2. Compare the disadvantages of different PC operating systems. > Windows: ugly interface, especially Win11, which blatantly copies macOS but poorly; not suitable for development; many vulnerabilities due to the x86 tax. > macOS: closed ecosystem, lack of software compatibility. > Linux: several distributions listed (Ubuntu, Debian, Open SUSE, Kali, Arch); not friendly to beginners, difficult environment configuration, few entertainment apps. > Chrome OS: I did not think of it at that time. Its disadvantage is heavy reliance on Google cloud services, which are unavailable here.

  3. What should be noted when collecting human data? > Right to know, privacy, ethics, comprehensive sampling (different genders, races, etc.), consideration of special cases (e.g., people with disabilities), elimination of external interference during collection, multiple trials to reduce errors.

Then came the Q&A session. Teachers reviewed the submitted resume and certificates and asked targeted questions:

  1. Do you have intended supervisors? > Yes, two supervisors in computer security (I had only viewed their homepages and presentations, not contacted them yet).

  2. Among your many projects and awards, which one is the most noteworthy?

  3. You have participated in many competitions. What do you think is the difference between competitions and scientific research? > Competitions solve defined problems in a short time; research explores problems over a long period.

  4. Why choose SUSTech instead of your home university or a closer school? > I felt the teachers might not be fully confident in their own school. I briefly explained my selection criteria, mentioned that my home university was moving to Xiang’an, and shared that I had visited SUSTech and enjoyed its campus atmosphere and environment.

  5. Following the previous question: In actual research, do you prefer defined problems or finding your own problems? > A middle ground: given a relatively specific direction, find problems within that scope.

I received the Excellent Camp certificate five days after the interview. Because of question 4, I felt the teachers lacked confidence, so I decided to prioritize my home university and put this offer aside without contacting the supervisor. As the earliest interview, it served as good practice for later ones.

4. Xiamen University (Home University)

Next was my home university. On the first day, the programming test had three beginner‑level C programming problems. I finished AK and left one hour early.

  1. Spiral matrix filling from outside to inside.
  2. Maximum subarray sum; small dataset allowed an O(n²) prefix sum brute‑force solution.
  3. Graduation photo arrangement: tallest in the middle, shorter ones on either side. Essentially sorting with satellite data; small dataset allowed a handwritten O(n²) selection sort.

Then came the presentations. The day before the camp opened, I contacted a new networking supervisor at my home university. We met after the presentations, and I told him I would consider the home university if I couldn’t get into NJU.

In the afternoon, there was a written test on Data Structures, basically a past final exam paper. Having practiced and known the patterns, it was not difficult, especially since I had scored 99 in Data Structures back then.

Finally, the interview, about 15 minutes. I needed to print my resume and prepare a self‑introduction PPT. My resume covered knowledge & skills, education, academic competitions, honors & awards, and social work. The PPT followed the same structure, and I added a “One More Thing” slide in the style of Apple events to showcase my photography hobby, demonstrating a good attitude and not being overly competitive.

There were five interviewers, four of whom had taught me, so we were familiar. First, a 1‑minute English self‑introduction, then a 5‑minute Chinese PPT introduction, followed by questions:

  1. English question: What gains from ACM competitions can be applied to future research? > Advanced algorithms and data structures, as well as teamwork. > Advanced Algorithms and advanced data structures, plus team communication and cooperation.

  2. A question about a project on my resume.

  3. A question about the details of a cybersecurity competition on my resume.

  4. Ideological and political question (I had to complain that my home university actually included such questions): What should be noted when speaking online?

None of the five teachers specialized in networking. After a moment of silence, they asked no further professional questions… The interview ended quickly. A week later, I ranked third and received an Excellent Camp certificate for an academic master’s spot (only 12 spots available, mostly for home university students).

5. Nanjing University (NJU)

Competition at NJU was indeed fierce. Even before formal admission, due to the large number of applicants, an online written test was required for preliminary screening.

The written test consisted entirely of closed‑book multiple‑choice questions, covering Data Structures, Computer Networks, Computer Organization, Operating Systems, and UNIX. There were 28 questions to be completed in 60 minutes, including 5 multiple‑response questions (the number is correct as I recall). The questions were difficult and detailed, such as:

Data Structures

  1. For a tree with maximum degree (n), where (m_i) is the number of nodes with degree (i), find the number of leaf nodes.

    Let (x) be the number of leaf nodes. From a graph perspective, the sum of degrees of all vertices is

    x+\sum_{i=1}^{n}(i+1)m_i-1

    (-1) because the root has no parent. The total number of vertices is

    \sum_{i=1}^nm_i+x

    Since a tree satisfies edges = vertices − 1, and edges = degree sum / 2:

    x+\sum_{i=1}^{n}(i+1)m_i-1=2\left(\sum_{i=1}^nm_i+x-1\right)

    Therefore

    x=\sum_{i=1}^n(im_i-m_i)+1=\sum_{i=2}^n(im_i-m_i)+1

  2. Process of Shell sort and merge sort.

  3. Topological sorting algorithm for a DAG; complete the algorithm steps. > Find vertices with in‑degree 0, enqueue them, remove outgoing edges, and repeat.

Computer Networks

  1. Judge which are valid Class B host addresses. > Starts with 10, corresponding to 128–191. Note that all‑1 host bits are multicast and cannot be used for hosts, so an option like 172.x.255.255 is invalid.

  2. CSMA/CD principle: Given frame length, transmission rate and propagation rate between A and B, compute the maximum link distance between A and B. > CSMA/CD requires that a collision is detected before transmission finishes. In the extreme case, A is about to finish sending and detects a collision from B. > >

  3. True/false questions about DNS A, CNAME, MX records.

Computer Organization

  1. Given a 5‑stage pipeline diagram, compute how many cycles the next instruction stalls for a branch instruction. > In the diagram, the branch address is written to PC in the MEM stage. So the next instruction waits for ID, EX, MEM: three stall cycles.

  2. For a direct‑mapped cache, given block size, number of cache blocks, number of main memory blocks, compute the total cache capacity (including tag overhead). > Essentially compute the number of tag bits. > > First compute main memory size from cache block size × main memory block count to get total address bits. > Block offset bits from block size. > Cache line index bits from number of cache blocks. > The rest are tag bits. > >

Operating Systems (UNIX)

  1. Comparison between ULT and KLT; true/false.

  2. 4GB virtual address space: how many levels in a multi‑level page table? > 2 levels: 4KB → 4MB → 4GB > >

  3. Can file descriptors (fd) be duplicated? Do they share offset after duplication? Do parent and child processes share fd and offset after fork? > Can be duplicated by dup; offset is shared. > > > > After fork, parent and child do not share fd, but still share offset. > >

  4. Parameters of the mmap system call. > I hadn’t studied this and guessed blindly. I should have selected all 6 options… > > c > void *mmap(void *addr, size_t len, int proto, int flag, int fd, off_t off); >

I felt terrible after the test and thought I would fail. Surprisingly, I was admitted five days later. I happily emailed the intended supervisor, only to find that he knew my home university supervisor, who then recommended me directly. The NJU supervisor replied that many students applied to his group and to contact him again after the interview…

I had bought a flight from Xiamen to Nanjing on the 23rd, planning to visit a few days early. However, two days before departure, a COVID‑19 outbreak occurred at Nanjing Airport, and the interview was moved online to the 28th… Online interviews were more convenient; the planned offline programming contest was canceled.

The online interview had four teachers, all with cameras on, lasting 15 minutes: 1‑minute English introduction, then questions:

  1. English question: Introduce the curriculum of your favorite course (choose one from DS, CO, CN, OS) in English and explain why. > I chose Computer Networks. For such technical courses, it is essential to review English textbooks to know professional terms. > I described the network topology and the TCP/IP model using a top‑down approach: application, transport, network, link, physical layers, listing protocols for each, and finally security, cryptography, hash, digital signatures. > Reason: powerful. Computer networks brought us face‑to‑face during COVID‑19.

  2. Since you chose CN: differences between TCP and UDP. Is Tencent Meeting TCP or UDP? Is WeChat messaging TCP or UDP? > TCP: connection‑oriented, reliable transmission, flow control, congestion control. > UDP: connectionless. > Tencent Meeting audio/video uses UDP; control signaling (meeting ID/password) uses TCP. WeChat messages use TCP.

  3. Awards in mathematical modeling and your role. > M award in the American Mathematical Contest in Modeling and second prize in the national contest; mainly responsible for programming.

  4. Since you mentioned cryptography in the English introduction: process, advantages, and disadvantages of symmetric and asymmetric encryption. > Symmetric encryption: shared key, relatively lower security, fast computation. > Asymmetric encryption: public/private key pair. Alice encrypts with Bob’s public key; only Bob’s private key can decrypt. High security but slow. > Therefore, in protocols such as TLS, asymmetric encryption is used to exchange the pre‑master secret, then symmetric encryption is used for efficiency.

  5. Any interested research directions? > Stated the direction and lab of the supervisor I had contacted.

  6. How do you relieve stress during competitions and projects? > I don’t feel much stress because I’m interested and have a good attitude. I relax by walking by the sea, hiking, and sightseeing in the city.

Although only 15 minutes, many questions were asked. I felt the interview went well, and a week later I received an Excellent Camp certificate for an academic master’s. I contacted the supervisor again and confirmed my spot in the lab, pending formal confirmation in October.

The supervisor asked about my ranking; I said exactly 10/100. He replied that I was lucky, as their initial cutoff was the top 10%… It seems that for younger students aiming for top schools, ranking is crucial; otherwise, you may not even get admitted to the summer camp.

EOF