BlackRock Interview Experience | On-Campus Internship 2020

First Round (Online Test) The online test had three sections

1. Software Aptitude: The questions were based on system design. The problem was described and, system designs were given in the form of flowcharts. MCQs were based on the flow of the system.
2. Data structures and algorithms: This round mainly had questions on trees.
   1. Inorder, postorder, preorder traversals
   2. Output-based questions on trees. Recursive functions were given, and you had to determine what that function did or what would be the output.
   3. Questions on AVL tree construction. The code for AVL Tree construction and an array of non-unique integers was given(It wasn't specified in the question that the code is for AVL Tree construction. You had to find out by analyzing at the code). The question was to find out the height of the tree.
3. SQL Section: It had 25 SQL questions. Pretty standard stuff. Some involved choosing the correct SQL query. Six or seven questions involved the DUAL table. I recommend you to read about it as it is not the most conventional topic to prepare for OTs. https://www.oracletutorial.com/oracle-basics/oracle-dual-table/

Approx 130 students were selected for the interview process. (The tech interviews were held on Cisco Webex) 2nd round (First Tech interview): My panel had two members. Both males. They introduced themselves and asked me to do the same. 1st Interviewer:  So tell me about your projects?

• I told him about the 3-4 projects that I did in my college. My projects involved database management systems, android development, and computer networks.

1st Interviewer: Tell me about your internship, and what was your role there? 1st Interviewer: Tell me about some of the features of the app. I don't want the specifics. Just an overview would be fine. 1st Interviewer:  How did you make the app secure?

• I told them about obfuscation and authorization of the users by verifying their id tokens before they make the API calls. He was satisfied with my answer. After I was done explaining my answer, he suggested that authorizing the user every time before making an API call would increase the number of server requests, so ideally, it would be better if I make the id token valid for a fixed period.

2nd Interviewer: How comfortable are you on the database side? Could you tell me how you would get the second highest salary from a salary table which has two columns named salary and employee name?

• They asked me to share my screen and write the SQL query on a word document. I gave them one approach by using the NOT IN operator. He then asked me not to use the NOT IN operator. I simply replaced the NOT IN operator with a '< '. He said both are correct, but he still wants a different approach. I gave him some ideas which were in the right direction, but I wasn't able to provide him with the exact query.

1st Interviewer: Which language do you code in?

• I said Java.

1st Interviewer: Can you write the code to implement a stack using an array.

• I wrote the code and explained the time and space complexities. https://www.geeksforgeeks.org/dsa/introduction-to-stack-data-structure-and-algorithm-tutorials/

1st Interviewer: Suppose you have an array of a billion numbers. Which sorting algorithm would you use?

• I asked whether extra memory is provided or not. He asked me to answer for both the cases. I said to him that if extra space is required, then I would use Merge sort since it has a constant O(nlogn) time complexity, and if additional space is not provided, then I would use quick-sort. I explained to him how the time complexity of quick-sort is O(nlogn) in the best and average case, and O(n^2) int the worst-case scenario. The interviewer was satisfied with my answer. It completely slipped my mind that you can perform in-place merge sort too :p

1. https://www.geeksforgeeks.org/dsa/merge-sort/
2. https://www.geeksforgeeks.org/dsa/quick-sort-algorithm/
3. https://www.geeksforgeeks.org/dsa/in-place-merge-sort/

1st Interviewer: Solve this puzzle An eccentric professor used a unique way to measure time for a test lasting 15 minutes. He used just two hourglasses. One measured 7 minutes and the other 11 minutes. During the whole time, he turned the hourglasses only 3 times. How did he measure the 15 minutes? I took 2-3 minutes to think and then explained my solution. He was satisfied with my answer. 2nd Interviewer: Do you have any questions for us?

• I asked them about their intern to full-time conversion rate. They said they don't have any specific percentage or number. He said that if you do your job well, we'll give you a full-time offer.

After half n hour, I got an email from Blackrock stating that I have qualified for the next round. 3rd round (Second Tech Interview): For this round also there were two-panel members: one male and one female. 1st Interviewer: Tell me about your DBMS project.

• I described the specifics to her.

1st Interviewer: How would you scale up this project?

• I explained how I'd shift from a 2 tier to a 3-tier architecture.
• Reduce data redundancy
• implement a load balancer
• I told her that for faster reads, I'd shift to a NoSQL DB and use RDBMS only for transactions.
• I explained to her how I would use database sharding.

1st Interviewer: Tell me about one incident in your past (not necessarily work-related) where you faced different obstacles and challenges and how did you overcome it. 1st Interviewer: How comfortable are you in DS and Algo, and which language do you code in?

• I told her that I'm not an expert, but I'm certainly comfortable.

1st Interviewer:  Suppose there is a spreadsheet and, you have multiple columns in it. The name of the columns are in the following pattern A | B | C | .............| Z | AA | AB | AC ............ | AAA and so on.  Can you explain how you would find the column number if I gave you the name of the column as a string?

• At first, I was a little confused about some parts. So I asked her to repeat the question. After she was done repeating the problem, I took 3-4 minutes to think about the approach. Whenever there was a doubt, I asked her about it.  After another 2-3 minutes, I was able to give her a proper approach.

It's always better to say out loud what you're thinking. It gives the interviewer a better idea of your problem-solving skills. Make sure you clearly understand the question. Don't hesitate to ask doubts. 1st Interviewer: Solve this puzzle, can you make 4 triangles with  6 Match sticks

• I know it's an easy one, but I wasn't able to solve this during the interview. After a few minutes, she discussed the solution with me.

1st Interviewer: What do you think is the difference between a Linked List and an Arraylist. What type of problems would you solve by using a linked list, and why would you prefer it over an ArrayList? Answered. You can check the answer here https://www.geeksforgeeks.org/java/arraylist-vs-linkedlist-java/ 2nd Interviewer: Where do you see yourself in 5 years? 2nd Interviewer:  Can you assess your last round? What were your strengths and weaknesses?

• I decided to answer this question with full honesty. I mentioned the areas where I struggled and the areas where I was comfortable.

1st Interviewer: Do you have any questions for us?

• I asked her how did I perform. On hearing my question, both of them chuckled softly and told me that the results for the next round would be shared with me shortly.

3rd round (HR Interview): There was only one HR guy. These are some of the questions that he asked me:

1. "I'm sorry I missed the company's pre-placement talk last night. Can you summarize it for me?"
2. "Do you know anything about finance?"
3. "Where do you see your self in 5 years"?
4. "Why do you want to join BlackRock?"

I told them about my seniors' experiences and how highly they speak of the work culture there. I gave him a few more reasons. I recommend you guys to visit the company's website before sitting for the interview. It always helps to know about the company's achievements and milestones.

1. "What do you find interesting in BlackRock wrt to Tech?" I mentioned their platform Aladdin. He was impressed with my research.
2. "Do you have any location preferences?"
3. "Do you have any questions for me?"

I asked about how his experience has been working for BlackRock. Verdict: Selected Tips:

•  Always be calm and listen carefully to what the interviewer is saying. Don't rush to answer the questions even if you know the exact answer.
• Always ask doubts about parts of the question you don't clearly understand.
• Research about the company. Always try to visit the company's website before the interview.