# DE Shaw On-Campus Internship Interview Experience 2019

Round 1: [Aptitude]

DE Shaw came to our campus for internship program that they have every year commonly called SIP (summer internship program).

250+ people sat for aptitude round including all electrical branches.

CGPA cutoff was 7 for COMP and IT and cutoff of 7.5 for other electrical branches.

Test was held on hackerrank platform.

4 sections for this round

Section 1  Coding question  (20 min)

We had to solve a coding question in 20 minutes for 20 marks.

Given a list of string. Each string of the form s1-s2, where s1 is a computer connected to s2 and vice versa. If a hacker attacks one of your computer, then its connected computers will also be hacked and in turn its connected computers will also get hacked just like chain reaction. We have to find maximum count of computers that will get hacked.

My solution :-

Declare a set of strings.

Traverse the list (in python) or vector (in c++), now for each string separate those strings as s1 and s2 and just add these strings to set.

We are using sets to avoid duplicate entries (Set is implemented as red black trees which doesn’t allow duplicates).

So after traversing the array of strings, we have a set with all unique entries.

Now use a map<string, int> mp, basically map each string in set to a integer, by iterating over a set.

Now for each particular computer name(string) you have an integer associated with it.

Now again traverse the set of strings and now build an adjacency list from it (Remember it should be an undirected graph).

After building the graph apply BFS utility function starting from each vertex and find the maximum count we can get and keep track of visited vertices to avoid cycles.

That maximum count is the answer.

Section 2 Technical MCQS (20 min)

DSA and DMBS mcqs. 10 MCQS. Each MCQ 2 marks.

These were easy as compared to Quant questions.

Section 3 Quant MCQS (20 min)

10 MCQS. Each MCQ 2 marks. I didn’t perform well in this, I think I was able to do 2 questions correctly and didn’t attempted remaining questions as there was negative marking. Questions were tough. More difficult than RS Agarwal questions.

Section 4 System MCQS

6 questions (Don’t remember the actual weightage, I ignored this section)

I didn’t know anything about system, so none of the question was near to what I know.

[Tip :- I would suggest try to do coding question correctly and ans some of the technical mcqs correctly and that’s enough. If you choose quant, then it would be little tough, and for system, it will depend on whether you had that course before or not. Target Hackerrank, to get control over coding  question. And don’t ever think about C language, it is near to impossible to complete the code using just C and building each data structure from scratch. So you have to use STL and that’s how question will be completed in 20 minutes]

Outoff 250+, 16 were selected for the interviews which were to be conducted next day.

Round 2: [Technical Round 1]  (50 min)

Q1)  Explain the approach of coding round question.

Q2) Given a queue q1 with elements and an empty queue q2. You need to reverse q1 by using q2 or by using nothing.

No, you can’t use recursion. Using recursion is equivalent to using stack.

Q3) What is binary search tree ? What is balanced binary search tree ? How will you balance a non balanced tree ? What is that process call ? (ans :- rotations)

Q4) What is error 401 ?

Q5) How https works ?

Q6) One of your friend is getting UI of particular website, but you are not, so what is the problem, how will use you diagnose it?

Q7) Questions on project. I did RSA encryption algorithm project, so they asked questions on that. Be sure you know all the proofs, basis and other things about your project. They wanted just simple things to know about project. For RSA it is asymmetric key cryptography, proof is based on number theory (Chinese Remainder Theorem and Fermats Little Theorem). Encryption is based on the fact that it is difficult to factorize a 100 digit (or any large length) product of prime numbers, it is mainly used by web browsers. So you should be knowing more things about your project rather than just knowing the algorithm.

Q8) Puzzle. Given 10 stacks each stack contains 10 coins of 1 gram each. But one stack all coins with weight 9 gram. You have a weighing machine. You have to find the faulty stack in minimum number of weighings ?

– Here first talk about the worst case, don’t directly jump to the optimal solution. So, in worst case you will require 9  Now after this try to think about optimising it. For best case, you just need one weighing. Take 1 coin from first stack, 2 from second, 3 from third and so on and weigh them together. If there was no faulty stack, then this weight would be 550. Now if weight is 549 then 1st stack is faulty, if 548 then 2nd and so on.

Q9) Puzzle https://www.geeksforgeeks.org/puzzle-21-3-ants-and-triangle/ . I was asked for four ants and a square.

Q10) What is git ? All git commands that I know ? Difference between push and commit ? What are branches in git ? Why use git ?

Q11) Do you any questions for us ?

Out of 16,   6 where selected for next round.

Round 3: [Technical Round 2] (15 min)

Q1) Again first question was based on online coding round question. Why did 2 test cases failed in the online coding round question? Why did you used C++ over Python for coding round?

Q2) Discussion on projects. Using my project concept, I gave them a use case for DE SHAW and they looked impressed.

Q3) What was the motivation for few projects that I mentioned ? (Be sure that you know your projects well)

Q5) Do you have any questions for us ?

This interview round was very fast.

I thought that this round will also have many questions as in Technical Round 1, but here I explained Q2) nicely, they look impressed and one of the interviewer said that he had no more questions, and so the second interviewer asked me Q3) and Q4)

This round was very straightforward and easy.

All 6 people had to attend HR.

Round 4: HR (5 min)

Q1) Tell me about yourself ?

Q2) What do you think about does DE SHAW do ?

Q3) Do you have any questions for us ?

Out of 6, 2 were selected for the internship, I was lucky enough to be one of them.

[Suggestions :-

Practice on  hackerrank to clear coding question in Aptitude Round.

Use geeksforgeeks to get control over all the DS Algo questions. Also follow puzzles on geeksforgeeks as there are some pretty good standard puzzles on geeks.

Be energetic. Ever  company want only energetic people. Be sure to fill yourself beforehand as the whole selection process takes place within 24 hours.

In the  interview be comfortable and don’t be nervous (although I was nervous). Remember interviewers are present to help you to get the job and not to throw you out of the selection process. There was a panel of 5 people (2 in 1st tech round, other 2 in 2nd tech round  and remaining one was HR), all of them were very cool and they kept smiling at regular intervals.

Best of luck !!!!

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