# D. E. Shaw interview experience for internship (On Campus 2018-2019)

Round 1:

This was a coding round. There were two coding questions on the online platform(Hackerrank). Test Duration was 50 minutes.

First Question

You are given a string of HTML tags with opening and closing tags, we have to find the maximum number of total tags where we group the same tags together and count them. Here the tag is defined as one opening and one closing tag where the order of opening and closing tag is irrelevant. Opening tag is defined as text written inside angular bracket (<tag>) and closing tag is defined as text written inside the angular bracket followed by (</…>)

Sample Output: 3

Explanation :

Total 3 head tags and 2 body tags, so answer is 3 i.e. max of 2, 3.

Here the point to be considered is that the tag is either opening followed by closing (not necessarily consecutively) or closing followed by the opening tag.

Second Question

Find the number at kth index in the ith permutation of first n natural numbers. Inputs are given in order of n,  i, k.

Sample Input: 3 2 2

Sample Output: 3

Total 22 students were selected for the next interview round.

Round 2:

This was the technical round and lasts about 1 hour 45 minutes in which they asked why did your second question in online coding round didn’t work. I told them about a minor flaw in my code.

The further questions in round 2 were:

1. You are given an n*m grid with some cells which are empty spaces, some of them were on fire and some of them were having walls. There was a person standing on a given cell and an exit at the rightmost bottom cell. The fire spreads in the four directions every second in the grid if the cell in the direction of propagation is the wall otherwise, it stops at that cell. The person can travel in empty space in the four directions every second. You have to find whether the person can escape from grid safely.
2.  Make the doubly linked list more memory efficient. Basically, you have to reduce the number of pointers per node from 2 to 1 and still be able to traverse in both the directions.
4.  Difference between a pointer and a reference. Why is pointer used in all traditional data structures (like linked list and trees) and not reference?
5. Given the unbalanced parenthesis string. You have to delete the minimum number of parenthesis to make it balanced and print all balanced parenthesis after deleting those minimum number of parenthesis.

Round 3:

It was also the technical round. It lasts about 1.5 hours.

Question asked in this round includes:

1. N/4 majority element problem. They gave me a real-life situation and the solution boils down to find all the elements in the given array which occur more than N/4 times.
2. Hashing, Collision, Collision Resolving Techniques, Fast Hashing in the situation of separate chaining.
3. Web Browser Designing Problem. You are going to design the web browser and you want to implement the feature of going on back and forward tabs. How will you implement that?
4. Minimising the cash flow problem.
5.  Some theoretical concepts of C++ like Dangling Pointer, Void Pointer, Out of memory Error (Don’t confuse it with array out of bound exception), What is core dumped in Segmentation Fault?, What are the differences between process and program, How a program become a process?.
6. Basic concepts of DBMS like Keys, Normalisation etc.
7. Questions on some easy queries of SQL which includes the concepts of joining tables, difference, and the intersection of different queries etc.

Round 4:

It was the HR round and she asked me questions like :

2. How much GPA did you get at the end of your first year?
3. How frequently you read the newspaper?
4. What do you know about D.E.Shaw?
5. How much do you rate yourself on the scale of 1-5 on G.K?
6. She gave me a puzzle. Which was formally defined as “You are given 8 identical looking balls. One of them is heavier than the rest of the 7 (all the others weigh exactly the same). You are provided with a simple mechanical balance and you are restricted to only 2 uses. Find the heavier ball”.
7. Are you good with numbers? She gave me a simple problem which was to find the last digit of 133^9.
8. Are you comfortable to shift to Hyderabad office if given chance to intern there?

Result: Selected

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