Recent posts in Interview Experience

101

This is the rough work I did during the interview, the question were added in a separate post (https://gateoverflow.in/blog/10800/iisc-csa-research-interview-questions)  as I did not want to reveal hints in the original post (perhaps open the questions side by side to make sense of the following rough work)

CSA prof 1 (not everything is correct in my solution): 

 

 

CSA prof 2 (not everything is complete in my rough work):
 csa_prof2

Feel free to ask in the comments, I am sure, some of the answers are not complete as the prof. just asked to explain some bits instead of writing everything down. 

mkagenius posted in Interview Experience Aug 25, 2020
2,950 views
102

The interview was conducted over Zoom video conference with 2 professors present. After the introductions, the following problems were asked from my selected topics – 

  • Probability theory and Discrete Mathematics. 

 

Professor 1 on Probability Theory ( Time: 20 mins including introductions)

  • Do you know what is a random variable?
  • Can you define it precisely? 
  • Now suppose you have a biased coin with the probability of a Heads being $p$ and the probability of a Tails being $(1-p)$ . How do you mathematically write the random variable for this?
  • Now suppose we are doing an experiment where we toss the same coin $N$ times. What is the sample space of this? 
  • What do you mean when you say Binomial distribution? 
  • Can you find the expected value of heads for above problem ($N$ tosses of the given biased coin)?
  • Okay, do the derivation.
  • Is there any other method to find it? 
  • Why do you say that you can add expected value of Bernoulli random variables?
  • Do the experiments need to be independent (for us to be able to add them to get the expected value)?
  • Calculate the expected value via the second method.

 

Professor 2 on Discrete Maths (Time: 15 mins)

  1. You are given $n$ vertices. Each pair of vertices $(v1, v2)$ are connected via an undirected edge. How many edges will be in the graph if self loops are allowed? 
  1. Suppose there are $n$ vertices and $e$ edges in an undirected graph. Can you say anything about the sum of the degrees of the vertices?
  1. Suppose I tell you that $n$ is odd and each vertex has an odd degree, is it possible? Can you write the explanation.
  1. Write down $a^2 + b^2 + 2ab$ $<=$  $k*(a+b)^2$ on the paper. Here $a,b$ are non-negative real numbers. Can you say anything about $k$?
  1. Now change it to $a^2 + b^2 + 2ab$ $<=$  $k*(a^2+b^2)$ . Can you say anything about $k$?

 

Hints: https://gateoverflow.in/blog/10821/my-rough-work-during-the-interview-for-csa-research-iisc

mkagenius posted in Interview Experience Aug 18, 2020 edited Aug 28, 2020 by mkagenius
3,726 views
103

Interview Experience for M.Tech. RA A.I. in I.I.T. Hyderabad

My interview was in July, 2020. It was conducted on google meet online due to COVID-19 pandemic. There were two rounds of interview. the first round was in the morning and second round was conducted on the same day after 3:30 pm.

Round 1:

I don’t remember the faculty name but there were 2 teachers in my panel.

P1: Introduce yourself and tell the topics of your interest in basic mathematics.

I was confused with basic mathematics and told Linear Algebra. But then the clarified and asked mathematical topics from class 9th and 10th like lines, triangles, etc. Then I choose geometry.

Ques1. Draw a graph of mod(x) + mod(y) = 1

Initially I drew it wrong as a circle but later I corrected it as a square.

They asked if I was comfortable in probability, though i never revised after GATE but had no other option and said yes

Ques 2: If you are given a bag in which you have 6 white balls and 4 black balls and you draw a ball and it is known as black and you throw it away. Now tell the probability of getting a black ball.

I tried solving it using Bayes theorem initially, but prof confused me if I already know that the ball was black then why are we using conditional probability. At that moment I got confused and choose 3/9 as my answer.

Ques 3: what is uniform distribution?

I defined both continuous and discrete distributions as I could not remember uniform distribution so later prof asked me to draw the graph of uniform distribution between -a to a. I could not draw at that time.

Later result was out around 2pm and I got selected for round 2

Round 2 Panel included 3 teachers: Prof Maunendra, Prof P. K. Srijith and Prof P. RAJALAKSHMI.

I was asked about my educational background and any project or course that I have done in BTech or otherwise related to Artificial Intelligence or Machine Learning.

I told about my BTech final year project as an application of NLP and they asked further details about the same.

I also mentioned doing one course on NLP so he asked me about my learning from the course and few questions related to that.

Later he gave me a question on probability which was as follows:

Ques1: If a company decides to have a lottery and distributes 50 tickets at Rs 10 each and there is a probability of winning as 0.2, also on winning the company gives Rs 40 to every winner (there can be more than one winner) then what is the total profit for the company and Is that profit fixed or can be changed?

I answered 100 and fixed( which i later guess was wrong ans this 100 would be the max probable value for profit but it can change).

Ques 2: The next question was to tell the difference between quicksort, insertion sort, selection sort and mergesort

I told that Merge sort is not in-place and uses O(N) space complexity while other algorithms change in the same data structure and has O(1) space complexity.

After 2 days we got the list of available projects and we filled our preferences. The selection was based on preference and performance in the interview.

Result: Not selected

Tip: Prepare probability and at least know few names of algorithms in ML. That will show your interest in the field. I only prepared Data structures and Algorithms and they asked only 1 question from that.

Shivangi bithel posted in Interview Experience Aug 16, 2020
2,765 views
104

Interview Experience for M.Tech. RA C.S.E. in I.I.T. Hyderabad

My interview was in July 2020. Due to pandemic it was taken online on Microsoft Teams. It was taken by two professors in my panel say P1 and P2.

P1: Hello Shivangi. I am Prof Sathya Peri from CSE Dept. Show your ID Card.

(shown)

P1: Start with your introduction and educational background.

(told)

(As i was working for 1 year now in IT sector so he asked)

P1: Why are you interested in M. Tech. ?

(told)

P1: As we are short in time so we will ask questions now, just explain the concept and don’t write the code for it.

P2: How can we find the middle element in the linked list in O(N) and only one traversal?

As length of the linked list was not given and only one traversal was in condition so he gave me hint to solve with one slow and one fast pointer…solved at last

P1: How can we print values of a BST in decreasing order?

As Inorder traversal of a BST is ascending order so i initially put that in an array and then reversed the array…but later improved the traversal with modification as we can print like Right, Root and Left and this will give descending order.

P1: Have you heard about the famous 2 SUM problem where a sum is given and we have to find pairs in the array which on addition gives that sum?

I knew the O(N) solution of this using hashmap and told him that…he was impressed with that and later he modified the question for BST and for that the similar concept can be used and i was able to solve that also.

Because of time shortage only these questions were being asked.

Result: Selected for Round 2.

Later they gave us a google meet link where they explained about available projects in M.Tech. RA and gave us a google form to fill with our preference by next day before Round 2 interviews.

 

Round 2: On Microsoft Teams

Interview was taken in 2 panels and as per my preference, I had to give interview in both the panels.

Panel 1: All professors with interest in ML and AI field were there.

  1. They asked for the introduction first.
  2. Why M. Tech. after job?
  3. Tell in brief about B. Tech. Project.
  4. What languages you know and how much experience in C/C++ coding?
  5. What is your research interest and then I said machine learning and NLP, so hey asked about any courses that I have done and name of classification algorithms.

Panel 2: All Professors with interest in systems were there.

  1. They asked for the introduction first.
  2. As per my preference in Networking project they asked me basic question from computer network like
    1. What do you remember in CN?… I stated with layers in CN.
    2. Which is your favorite layer?… I said Network layer
    3. He asked me about routing algorithms…Distance vector routing and Link state routing.
    4. Which one is better for large network and why?
    5. What is count to infinity problem?
    6. Experience with programming in college and work… I told about working on JAVA in my job…so he asked which packages do I use in java.

Result: Selected for M2Smart Project

Shivangi bithel posted in Interview Experience Aug 16, 2020
4,294 views
105

IIT Patna (Mtech in CS, Research Fellowship)

  1. What is the probability of getting 2 consecutive heads in a fair coin toss?
  2. What is the probability of getting a prime number when 1–10 is randomly sampled?
  3. What is the probability of getting a prime number given that the number chosen is greater than 5?
  4. You are given 2 unbounded numbers to add (assume that these 2 numbers can exceed the max capacity size_of_int of the given machine). Write a program to store and add these 2 numbers. (Hint. Use linked list)

IIT Jodhpur (Mtech in CS, Self Sponsored)

  1. Basic questions of Joint and Conditional Probability.
  2. You are given an array of size n from with consecutive integers but one number is missing. E.g. {1,2,3,5,6,7}. Write an algorithm to find this missing number. What is the running time of the best algorithm for this? Can you use the formula for the sum of natural numbers till n to design this?
  3. Define inverse of a matrix, mathematically and intuitively.
  4. When does a matrix not have an inverse?

IITH (Mtech in CS, Self Sponsored)

  1. F(n) = 100n; G(n) = n². F(n) = O(g(N)), is this true or false? In what cases is this true or false?
  2. You are given an array ‘a’ of size ‘n’, where all the elements are 0 except for 1 element which is 1. You have a function Sum(a, j) which return the sum of the elements of the array from i → j. E.g Sum(a,5) will return the sum of elements from a[1] to a[5]. Using Sum(), what is the least number of calls needed to determine the index r S.T a[r] = 1. (Hint: use divide and conquer)
  3. Given a polynomial P(x) = x⁵ + 4x³ + 6x + 5. Assuming you are given only one temporary variable t and the value of x, what is the minimum number of operations needed to compute P(x).
  4. A word of variable size is generated with random permutations of the alphabet a-z. What is the probability that the letter ‘a’ appears before ‘b’ (assuming that they appear only once). (Ans: 50%)

If this helped you feel free to like and share!

sharan21 posted in Interview Experience Aug 12, 2020
2,587 views
106
Due to COVID 19 pandemic this year Direct PhD selection only consisted of an online interview.

A mail was sent by the authorities regarding the shortlist about 10 days before the interview. My interview was scheduled on 23rd of July. They had previously asked us to select 2 favourite subjects from the list of Gate topics on which they could interview upon. They had also asked for Statement of Purpose of the research work.

Subjects selected: Operating Systems and Database Systems.

On the day of interview a professor called me half an hour prior to the interview and asked me to connect as soon as they allow. There were total of 9 professors for the interview, but only 4 professors asked the questions.

Prof 1: Give a brief introduction about yourself and your academic background.

Me: Answered

Prof 2: The topic you selected for research does not match with your favourite subjects. Why so?

Me: Answered

Prof 3: What is concurrency in Operating Systems?

Me: Answered

Prof 3: Why do we need concurrency?

Me: Answered

Prof 3: Give any applications where you have found concurrency necessary?

Me: Answered

Prof 3: Which operations need concurrency

Me: Answered (with respect  to Read/Write Conflicts)

Prof 3: What is race around condition? How do we ensure it any protocol/algorithm?

Me: Explained. Specified Peterson’s Algorithm. Prof 3 told to write the code to implement Peterson algorithm

Prof 3:  Any disadvantages of Peterson Algorithm? How can we overcome it?

Me: Answered. Explained about Baker’s Algorithm

Prof 3: Ok last question You know what atomic operation mean? Can atomic operations be practically implementable?
Me: Answered (Not sure though)

Prof 4: What are transactions? What difference you notice in maintaining concurrency in OS and concurrency in Database Systems.

Me: Defined and Explained.

Prof 4: What is consistency in ACID properties. Give a formal definition.

Me: Defined.

Prof 4: I give you 2 operation Fetch and Add & Compare and Swap operations. Both are atomic.Which one will you choose for synchronization and why so?

Me: Answered.

Prof 4: Gave 2 transactions with variables X, Y and asked the difference between serial and serializable schedule. Can the given transaction be serializable. If so how and if not why?

Me: Answered

Prof 4: What protocols could you use to ensure concurrency in transactions.

Me:  Locking Protocols (2 Phase Locking)

Prof 4: 2 Phase Locking can be applied to transactions I gave before. Can you brief out the proof that 2 PL ensures serializability.

Me: Answered whatever I knew. I did not remember the proof exactly but Sir was satisfied.

Prof 1: Write a program to find number of trailing zeroes ( Expected mostly in C)

Me:Answered

Prof 1: Your program should be written with function

Me: Modified.

Prof 1: How will you modify it if instead of n I ask you for n factorial.

Me: Told.

Prof 5: Your interests are in Cryptography. Tell me about the final year project.

Me: Answered partially. Sir wanted me to tell regarding the security parameters chosen to prove our model is secure.

Prof 5: Can you just prove formally empty set is a subset of every set.

Me: Gave an intuitive way. But was not satisfied.

 

Prof 1: You can leave.

The interview was nearly for an hour. The professors were expertized, kind and cooperative. The professors made the interview comfortable. It was a great interview experience from the professors of top most Institute in India.
Raghavendra_NV posted in Interview Experience Aug 9, 2020
1,211 views
107
The interview was scheduled on Microsoft Team application. Interview panel consisted of 2 members.

Prof 1: Give a brief introduction about yourself

Me: Answered.

Prof 1: What are the different search algorithms you know?

Me: Answered

Prof 1: What is the worst best and average case of binary search algorithm?

Me: Answered

Prof 1: Have u heard about ternary search. Explained it in a sentence and asked what is its complexity?

Me: Answered

Prof 1: Prove how binary search is better than ternary search

Me: Stumbled a bit.

Prof 2: Gave a probability question where there are balls numbered from 1-13 what is the probability that if you remove 2 balls uniformly at random the probability that their MSB is same.

Me: Answered

Prof 1: Can you prove or disprove the sentence. The minimum and maximum values are always present as leaf node in binary search tree.

Me: Answered

 

The interview was one of the shortest interviews experienced. The professors were very helping and cooperative. The interview was a great learning experience to me.
Raghavendra_NV posted in Interview Experience Aug 9, 2020
2,466 views
108
The AI department of IIT Hyderabad had shortlisted the candidates based on gate score and academic performance. They had selected around 40 candidates for the interview. Due to covid pandemic the interview was organized on Google meet. The interview was scheduled on 17 July 2020.The candidates had to be online at 10 am for document verification.

Documents were verified and I had to join the interview using a different Google meet link sent.

They were 3 professors in the interview panel.

Prof 1: Give a brief introduction about yourself.

Me: Answered.

Prof 1: So, which are your subjects of interest? Do you have a liking for probability and Linear Algebra?

Me: I told yes So, they started asking questions on probability and linear algebra.

Prof 2: What are independent events?

Me: Answered

Prof 2: How do you identify independent events? Formula for independent events & Bayes Theorem.

Me: Answered

Prof 2: Draw and show in Venn diagram 2 events A and B which are independent.

Me: Drew the Venn diagram.

Prof 2: So, from your diagram you mean to say independent events cannot be identified just by diagram?

Me: Yes, Sir We need to know the probability of intersection of A and B.

Prof 2: Create your own example for Independent event and explain how you will conceive that they are independent.

Me: Answered with respect to rolling of dices.

Prof 3: Have you taken up Linear Algebra in UG?

Me: Yes

Prof 3: Ok you are given a function and told to find minimum how will you find?

Me: Answered

Prof 3: In continuation to the question find the minimum of f(x)…

Me: Differentiated and told the points of minima.

Prof 3: Gave 2 vectors A and B and said find a 2*2 vector X such that AX=B

Me: Gave an answered directly and trial and error

Prof 3: I know you might have tried the values now what if it is 100*100 matrix.

Me: Understood and got the answer. The question was based on Eigen Vectors.

Prof 3: Asked a few questions on Eigen vectors.

The interview took around 25 minutes. Later on, the same day, I received a mail for round 2 of their interview. They had shortlisted 14 candidates.

Interview panel had 3 members. One of the professors was the same as round 1.

Prof 1: What are your UG projects?

Me: Answered

Prof 1: Your projects are based on Cryptography and Security, then why AI?

Me: Explained

Prof 1: What all do you know about Machine Learning?

Me: Answered

Prof 1: What are classifiers? Tell me some binary classifiers.

Me: Answered

Prof 1: What if I have multiple classes. You have studied multi class classifiers?

Me: Bit confused

 Prof 1: How can you make binary classifier to work as multi-class classifier ?

Me: Answered

Prof 1: Given 1 vs 1 and 1 vs all approach if there are 10 classes how many classifiers are generated?

Me: Answered

Prof 2: What is Logistic Regression. Why is it called Regression?

Me: Answered.

Prof 2: You said you know about KNN classifier. State the disadvantages of using it.

Me: Answered not quiet satisfied.

Prof 3: Given a double differentiation of the function is always positive. What can you infer?

Me: Answered

Prof 3: What are convex functions?

Me: Answered

Prof 3: Can you give me mathematically how logistic regression error function is derived?
Me: Not Answered

 

Prof 3: Thank you, we are done

 

The round 2 of interview was basically to check if we have prior knowledge about Machine Learning, though professors told that its ok to start from zero if anyone has not undergone ML during UG courses. The professors were very helping and cooperative. The interview was a great learning experience to me.
Raghavendra_NV posted in Interview Experience Aug 9, 2020
3,286 views
109
IIT Gandhinagar this year conducted the interview via Google Meet due to the prevailing pandemic situation. The mail is sent to the selected candidates for the interview nearly a week before the date of interview. On the day of interview, we need to login using our registration number based upon which a token number was generated. My interview was scheduled at around 11.30.

 The interview panel consisted of 2 professors.

Prof 1: Give a brief description about yourself

Me: Answered

Prof 1: Which is your favourite UG level subject?

Me: Operating Systems

Prof 1: What is Virtual Memory? Why is it needed? How is the addressing done?..

Me: Answered

Prof 1: What about registers? How are they addressed?

Me: Answered

Prof 1: Can registers have virtual addressing? Justify your answer

Me: Answered

Prof 1: Asked about the deadlock.What techniques are used to prevent the deadlock?

Me: Answered

Prof 1: What are the graphs called which are used to detect deadlock called? What does it tell you about deadlock?

Me: Answered

Prof 1: What are the different types of edges in DFS? How to identify loop?

Me: Answered

Prof 1: Give a logic to find middle most element in the linked list?

Me: Answered.

Prof 1: What is your UG project based on? Give an overall aim of your project

Me: Answered

Since my project include Dijkstra Algorithm there were a series of questions on Dijkstra algorithm, its working and how it fails.

Prof 1: What if edges are added by constant c or multiplied by constant c will shortest path change? What if we square all the edges? What is handshaking lemma? Maximum number of edges in graph with certain condition imposed was asked. Professor 1 also asked an informal proof for the answers given or an counter example to convince the answers given.

Me: Answered

Prof 2: Asked a few problems on mathematics. The focus was majorly on discrete maths. Some of the problems asked were

Proof that graph cannot have odd vertices with odd degree.

Number of ways rooks can be organized on a chessboard.

A path was shown on ppt and a honey bee has to move from starting point to end point.Number of ways it can do so.

Me: Answered most of the questions.

The interview was conducted for nearly 50 minutes. The faculties were excellent with respect to knowledge and were very much helpful.This made my interview experience to be comfortable with out any anxiety.
Raghavendra_NV posted in Interview Experience Aug 7, 2020
2,238 views
110

Name:- Ashish Seth

Gate Score:- 632

Category:- OBC-NCL

Primary Subject:- Linear Algebra

My interview was conducted on 22-July-2020. It was an online interview which was conducted on google meet. My interview started at 10:33 am and went till 11:37 am.

Interviewers:- I1,I2,I3,I4

myself: M

I1: hello Ashish

M: Good Morning Sir..

I1: how are you Ashish

M: Sir little bit nerves…

I1:(Smiling) you Know Ashish there is a magical thing called Water. Kindly drink it you will feel better.

(Every professor present in the panel started laughing. Till then all my nervousness was gone)

I1: Ok Ashish introduce your self.

M: I tried to include as many point which i could think of in my introduction.

  1. college name and current SGPA
  2. current final year project
  3. how much i like linear algebra.

 I1: you do know that it is not mandatory to do research on your selected primary subject but it is good that you like linear algebra because it is one the interviewer’s favorite subject.

I2:ok Ashish i think we can start off with a programming question. Write a function that take sorted int arr as a argument and return 1 or 0 to indicate the presence of duplicate.

M: It was easy for me so i did it in 1 min.

(than again I2 gave some modifiaction that were also simple)

I3: ok Ashish know we can switch to your primary subject.(He wrote a 4X4 permutation matrix(P) and a unknown matrix(U) and told me to do the product of two PU and UP)

M: Used column tech of multiplication for UP and row tech for PU.

I4: ok Ashish lets move on to next question do you no about rotation matrix and can you state 2X2 rotation matrix.

M: easly able to state and also told them some property like orthogonal matrix and rotation matrix will not change the l2 norm of a vector when multiplied.

I4 :(Next Question was kind of expected) prove how a rotation matrix will rotate any given vector.

M: prove with the help of dot product rule of two vector aTb.

I3:ok Ashish lets move on to next question. Lets say you have a Symm square matrix(A) do you know about its eigenvalues.

M: Sir they will be real.

I3: ok so now lets say we have a system define like this:

Ax=b than what about b ?

M: b must lie in the column space of A and its order will be nX1.

I3: ok so lets say you multiply A again and again to this system for m times where m is very large then what would happen.

M: i told him about symm matrix have complete set of eigen vectors so they are always diagonalizable. (we had about 10 min discussion regarding this fact where he gave me different rank matrices 1 to 3 and told me to check my statement on diff matrices). finally i was able to say that given eigen value of A being e, eigen value of A^2 will be e^2 and so on and the eigen vector will be same.

I3: ok ashish lets move on to next question given a matrix:

0.75 0.25

0.25 0.75   find its eigenvalues

M: (i was able to do it)

I3: Do you find anything special in this matrix.

M: Sir it is Symmetric and will have orthogonal eigen vector.

I3: Do you know about stotatic matrices:

M:(Never heard of it) No Sir.

I3: ok Ashish we are done from our side.

(After that i mentioned the interviewers about CS6015 course offered by iitm for Linear Algebra and how the Assignment and tutorials helped me).

 

One of the best day of my life was 1st Aug when result was declared and i found my name in MS(project) List.

 

 

 

 

   

Ashish16226 posted in Interview Experience Aug 5, 2020
986 views
111

IIT Madras MS In Computer Science And Engineering Interview Experience

Hello everyone. I recently gave an interview for an MS position in Computer Science and Engineering at IIT Madras. The interview was scheduled to happen on the 20th of July, 2020 within the specified time slot 09:00–13:30. My interview began at 10:30 AM.

Note: Due to the prevailing Covid-19 situation, the written test was canceled and the selection was solely on the performance in the interview.

Before the interview

Out of the 1937 applications received, IIT Madras shortlisted 192 candidates for the interview based on Gate Score and Undergraduate GPA/Percentage. The cutoff for Non-EWS General Candidates was 700 Gate Score and 8.0 GPA / 75% in Undergraduate. The candidates who were shortlisted were emailed a google form in which we had to mention a primary subject to be interviewed apart from Programming subject preferably in the C Programming Language. The primary subject ranged from topics in Computer Science (for eg., Operating Systems, Computer Networks, Computer Organization, and Architecture,etc.) to Linear Algebra, Probability Theory and Signals and Systems. I selected Linear Algebra as the primary subject to be interviewed in.

Interview

Out of 6 professors present in the panel. 3 of them interviewed me. Let’s call them I1, I2 and I3.

I1 : Tell me something about yourself.

Me : Gave a brief introduction about myself and my work experience.

I1 : OK, so we will start with Programming in C. I will hand over to I2 to start asking the programming question. He also shared a codeshare.io link so that I could write my code there in real-time evaluated by the panel members.

I2 : Hi Aditya, as you have selected Linear Algebra as your primary subject, your programming question is :

Write a function in C that takes two matrices as input and returns the matrix multiplication of them. Make sure the matrices taken as input are as generic as possible.

Me : Answered using Malloc for memory allocation and double-pointer approach. Just when I finished writing the functions and was about to write the main function, I1 interrupted…

I2 : I think that is fine. So, we can go ahead with the interview. (calls out I1).

I1 : Alright, so now I3 will be taking over your Linear Algebra interview.

I3 : Hi Aditya, so I see you have written a complex algorithm for Matrix Multiplication in which you have used this dot product formula to evaluate the cells, why not we can use matrix element-wise multiplication as a substitute for Matrix Multiplication and not this complex algorithm?

Me (numbed and thinking what a question he has just asked, wherein schools, you are taught to multiply two matrices with the formula given but never ever stumbled upon this):

I tried to answer the question to the best of my knowledge about Matrix Multiplication as Transformation and Composite of a function but the interviewer was not completely satisfied.

I3 : Okay, I am happy that you could relate it somewhat to Transformation but the answer lies somewhere else. Maybe you could think about it in your free time. The answer lies in the topic Relations, Discrete Mathematics.

Me : Okay, thank you, sir.

I3 : So, are you comfortable with eigenvectors and eigenvalues?

Me : Yes, sir.

I3 : Okay, so does eigenvalue exist for every rectangular matrix?

Me : No sir, it only exists for square matrices.

I3 : Does it exist for all square matrices?

Me : Yes sir, it exists for all square matrices.

I3 (trying to confuse me): Do you want to rethink your answer?

Me : No, sir.

I3 : Think again.

Me : I started explaining that if a matrix is singular, one of the eigenvalues will be zero and if it is non-singular then we can get eigenvalues for the given matrix.

I3 : Okay, got it. Now, do you know what is diagonalization of a matrix?

Me : Yes sir, we can write a given matrix as a product of three matrices. Let A be a given matrix, we can write A = B-1CB

I3 : Okay, I have no more questions. Over to I1

I1 : So, that will be it, Aditya. Our admissions committee will let you know of the results. Thank you for your time.

Me : Thank you, sir.

Overall, the professors were very friendly in there approach and never made me feel afraid of the interview. In all, it was a wonderful experience and the interview lasted for about 25 minutes.

Resources I used for Preparation

  1. MIT 18.01 SC Linear Algebra by Gilbert Strang
  2. Made Easy Engineering Mathematics Book for solving GATE Questions
  3. The C Programming Language by Dennis Ritchie, Brian Kerningham for pointer related concepts.

Verdict: Selected

 

 

aditya19 posted in Interview Experience Aug 4, 2020
1,460 views
112

Due to covid-19 pandemic,this year MS selection consists only interview via Google meet.they sent a mail about shortlist,schedule & list of subjects to choose in a google form a week before.My slot was on 20th July, 9:00 – 13:30, panel – 1.On 20th July morning I got a call from a professor of IITM to get ready for the Interview.My interview was scheduled around 12:30.Interview panel was of 5 or 6 professors,only 2 of them interacted with me.Nandivada & Janakiram.

Nandivada :– Introduce yourself & your academic background.

Me: – told.

Nandivada: – we’ll 1st give you a coding problem & then qsn from your chosen subject.

Define a linked list node structure which will store a char value.

Me:- defined.

Nandivada:- WAP to count number of nodes in a linked list

Me:- wrote the function.

Nandivada:- I have an allergy of while loop,can u please remove it & rewrite the code.

Me:- 1st time hearing some qsn from IIT professors & I was confused at that time & with some thinking I told them that I can use recursion but can’t write the code.(P.S – I’m not good at coding).after interview I found out it was damn easy & hit on my head.

Now suddenly Janakiram interfere & he also asked me a coding problem.

Janakiram:- Can u WAP to find a loop in linked list.

Me:- as I’ve said I’m not good at coding,so obviosuly I couldn’t answere this.

Nandivada:- okay,we’ll move onto your primary subject.

 

Now,Janakiram asked me some qsns from DBMS.

Janakiram:- What is transaction

Me:- Transaction is a set of operations to perform a task if I say by one line & it has some ACID property which every transaction have to follow.(then asked me full forms of ACID properties & I told).

Janakiram:- what do u mean by Isolation

Me:- told in my way which was partially correct,but he said this is not actually correct & after think for a while I told the corrcet definition.

Janakiram:- How Database manger ensure serilizability in a transaction.

Me:- totally forgot about to mention 2PL.

Janakiram:- Do u know 2PL ?

Me:- oh yes yes,there are two types of locking to ensure serilizability.2PL & timestamp.

Janakiram:- why is this locking called 2 phase & what are the 2 phases actually & what a transaction do in these 2 phases.

Me:- told it correctly.

Jankiram:- write the two transactions T1 & T2(gave me two transactions),write a concurrent schedule which is conflict serializable.

Me:- again confuesd & told the approach that if we can interchange the non-conflict operations,then we’ll get a conflict serilizable schedule & try to write a conflict serializable schedule……..

Janakiram:- what are the conflict operations in it.

Me:- told

Janakiram:- Give me a schedule w.r.t  T1 & T2 which allows 2PL protocol.

Me:- sir,If I can get a concurrent schedule then I can tell that it allows 2PL or not.(try to get a concurrent schedule for 2PL)

Janakiram:- (here he try to help me & gave me a two three lines of a concurrent schedule) Is it allows 2PL

Me:- No,because there are some exclusive lock for which it’s not allowed in 2PL.

Janakiram:- How 2PL ensure serializability.

Me:- Told about Lock point,if we follow lock point then we’ll get a serializable schedule.

Janakiram:- what is lock point ??

Me:- lock point is where the transaction gets its last lock.

Janakiram:- Okay I’m done.

Nandivada:- Do u have any query ??

I asked about the course & difference between Ms & Mtech & How is the job opprotunities of Ms.

 

Verdict – Not selected :(

My experience & tips for future aspirants :  Interview was I think average,they gave me hints wherever I was stuck or blank & they will try to make you comfortable during the interview.Overall it was a good experience from my side.

For future aspirants I will say that first of all Don’t confuse,because confusion & fear is the biggest enemy & try to respond with professors as much as possible because they will see your responsiveness & also try to understand what he/she wants from you,let them talk,don’t interrupt in middle.

For preparation,one should do coding form DS topicwise.GFG is good source.also prepare one or two subject very deeply,it will save you in interview.

 

 

mrinmoyh posted in Interview Experience Aug 2, 2020 edited Aug 2, 2020 by mrinmoyh
1,565 views
113

[ Prior to interview there was coding round containing 5 questions to be solved in 2 hours, I remember 3 of them as given,

1)Finding nth number in a tribonacci series(not given directly that it is tribonacci series but based on initial 7 numbers given, you’ll guess that) and also to take care of overflow for calculating with large values of ‘n’ to score full 100 marks.

2)You’ve a square $n\times n$ chess board, where each entry is either a building or empty, each entry can store 1 unit water when empty. If water is surrounded by buildings from all sides then only it is stored if there is any opening on any side then water will leak and water stored is zero unit, now given such an input square matrix with buildings on it represented by ‘*’, empty entries by ‘.’, calculate the amount of water stored. e.g.,

$\begin{bmatrix} .&*&*&.\\ *&.&.&*\\ *&.&*&.\\ .&*&.&.\\ \end{bmatrix}$would store 3 units of water. $\begin{bmatrix} .&*&*&.\\ *&.&.&*\\ *&.&*&.\\ .&.&*&*\\ \end{bmatrix}$would store 0 units of water.

3)There is an adjacency matrix of a graph, for any vertex, calculate absolute value of difference between in-degree and out-degree, print the larger value and the vertex that possess it. ]

Got the mail for clearing the coding test the same night and the interview was scheduled 2 days after.

I-Interviewer, M-Me

I- You’ve a complete ternary tree, number of leaf nodes are ‘n’, what’s the number of internal nodes?

M- We’ve this relation, $L=I\times(n-1)+1$  ($L$ and $I$ are number of leaf and internal nodes respectively, ‘$n$’ is the ary of the tree)

$n=I\times(3-1)+1$

$I=\frac{n-1}{2}$

The interviewer wasn’t satisfied with me using the direct formula so then I derived the expression and calculated, 

Suppose the height of the tree is h, $L=3^h$

$Total Nodes=L+I=3^0+3^1+3^2+.......+3^h=3^0\times\frac{3^{h+1}-1}{3-1}$

$L+I=\frac{3\times3^{h}-1}{2}=\frac{3\times L-1}{2}$

$2\times (L+I)=3\times L-1$

$I=\frac{L-1}{2}=\frac{n-1}{2}$  (No of leaf nodes are ‘n’)

I- Do you know there are some proof techniques (in algorithms or Computer science, don’t remember exactly which one he said)?

M- No.

I- You’ve two dice, probability that one is even, other is odd?

M- (I asked him if they’re identical, first he said yes then no)

In identical dice, pair (dice1,dice2)$\rightarrow$(a,b) & (b,a) are considered one event while in distinct they’re counted as two events. 

For identical,

favourable cases=$dice1\times dice2=(1,3,5)\times(2,4,6)=3\times3=9$

total cases=$(1)\times(1,2,3,4,5,6)+(2)\times(2,3,4,5,6)+(3)\times(3,4,5,6)+(4)\times(4,5,6)+(5)\times(5,6)+(6)\times(6)$

$=1\times6+1\times5+1\times4+1\times3+1\times2+1\times1=21$

$P=9/21$

For distinct,

favourable cases=$dice1\times dice2=(1,3,5)\times(2,4,6)+(2,4,6)\times(1,3,5)=3\times3+3\times3=18$

total cases=$(1,2,3,4,5,6)\times (1,2,3,4,5,6)=6\times 6=36$

 $P=18/36$

I- Probability that one is even given that one is odd?

M- Let $A$ be the probability than one dice is even and $B$ be the probability that one dice is odd,

$B$ will exclude only three cases (2,2),(4,4) and (6,6) so $P(B)=\frac{33}{36}$ [ B will also exclude (2,4),(2,6),(4,6),(4,2),(6,2),(6,4) cases which I forgot to include that time. ]

$A\cap B$ means one dice is even and one dice is odd which excludes six cases, (1,1),(2,2),(3,3),(4,4),(5,5) and (6,6), so [ will exclude 18 cases in total, (1,3,5)$\times$(2,4,6)+(2,4,6)$\times$(1,3,5)=3$\times$3+3$\times$3=18, I also didn’t take this into account during interview ]

$P(A\cap B)=\frac{30}{36}$

$P(A/B)=\frac{P(A\cap B)}{P(B)}$

            $=30/33$  Ans. 

I- How did you calculate?

M- I gave him the explanation and there were some more discussions and questions into the same and later the professor said that I missed some even even case or something like that, I guess the missed cases that I’ve mentioned before, don’t remember exactly.)

I- You said your research interest as Deep learning right?

M- Yes

I- Draw an AND gate with a single perceptron with activation function as

 $f(x)= +1, x>0$ 

         $ -1, x<0$

M-

 

I- Draw an XOR Gate with single perceptron?

M- (after some calculation and thinking) not possible with single perceptron.

I- Why?

M- Because there are complementary kind of cases like in AND (1,1) producing higher Σwx+b and remaining all cases produce lower but in XOR not like that.

[   the following answer I found on a webpage is quite appropriate- A "single-layer" perceptron can't implement XOR. The reason is because the classes in XOR are not linearly separable. You cannot draw a straight line to separate the points (0,0),(1,1) from the points (0,1),(1,0). ]

(A professor I showed interest in took my interview on phone call after some day of official interview, also he asked me if I can mail my CV)

I- You’re interested in medical applications of AI?

M- Yes.

I- Why you didn’t go for job having a high CGPA?

M- told about something being interested in research and what kind of research I like.

I- Have you done good coding things?

M- Yes.

I- Then, why is your score low in coding test?

M- I told about that there were too many questions with good difficulty level and even solving questions like that on codechef takes quite amount of time for me.

I- So given enough time you would’ve done all?

M- Hopefully more of them.

I- Then he asked me about what was asked in the interview, and since he wasn’t there on the interview panel that day he asked me if he can ask me questions and asked the following.

I- What is the max and min height of a binary tree, I want exact values?

M- (n-1) and $log_2 n$, Skewed tree for max and balanced tree for min.

I- What’ll be the answer if we put the following constraint, at any node, number of nodes in right subtree should be atleast half of the nodes in left subtree?

M- Same answer (n-1) and $log_2 n$, Right skewed tree for max and balanced tree for min still satisfy the given constraint.

I- What about the following constraint, at any node, number of nodes in right subtree should be atleast half of the nodes in left subtree as well as number of nodes in left subtree should be atleast half of the nodes in right subtree?

M- Min height is still same. Max height is $log_{(\frac{3}{2})} n$

[ $R\geq\frac{L}{2}\rightarrow L\leq2R$………….(i)

     $L\geq\frac{R}{2}$…………..(ii)

From (i) and (ii) we get, $\frac{R}{2}\leq L\leq2R$, so L can have min $\frac{R}{2}$ nodes, now choose one node as root out of ‘n’ nodes, let L and R be the number of nodes in left and right subtree

respectively for the root then,L+R=n-1, L=$\frac{R}{2}\rightarrow L=\frac{n-1}{3}, R=\frac{2\times(n-1)}{3}$

For max height again check splitting at the right subtree and so on...which give max height  $log_{(\frac{3}{2})} n$. Although this answer might be wrong and the professor wasn’t enough satisfied it seemed.]

I- What is the proof that your answer is correct, maybe distributing nodes half-half in both left and right tree at some points or as a whole produces max height?

M- Proof I don’t know. but this seems to be correct.

I- In a throw of a dice (a,b), $X$ is a random variable, that takes the larger value, i.e.,

$X=a,a\geq b$

      $=b,a<b$

calculate $P(X=i)$ in terms of ‘i’.

M- $X=1$ only in (1,1), $X=2$ only in (1,2),(2,2),(2,1), $X=3$ only in (1,3),(2,3),(3,3),(3,2),(3,1) and so on…

In general, $X=i$ only in $2\times i-1$ cases.

so $P(X=i)=\frac{2\times i-1}{36}$ (first did silly mistake and told $P(X=i)=\frac{i}{36}$ and then gave the correct answer.)

I- What if you’ve an ‘$n$’ faced dice?

M- Then, $P(X=i)=\frac{2\times i-1}{n^2}$

(P.S.:- Some my answers may not be correct so do check on that. My gate score-744, rank-460, so got shortlisted for coding test then for interview, and finally got the offer.)

 

Shivct1782 posted in Interview Experience Jul 31, 2020 edited Aug 1, 2020 by Shivct1782
3,890 views
114

Interview date: 23-07-2020

Round 1(written): Wasn’t conducted due to ongoing pandemic.

Round 2(Interview): duration of the interview was about 1 hour.

I was told that they will first ask some programming questions and then move to subjects which I was asked to select before the interview. The subjects were Data Structures and Database Systems.

Programming:

I: Write a program to find the largest element in a linked list?

M: They told to check some conditions. Initially, in line number 9, I wrote some mistake which I corrected later. 

#include<bits/stdc++.h>
using namespace std;
int findMax(struct node *ptr){
    if(ptr == NULL)
        return -1;
    if(ptr->next == NULL)
        return ptr->data;
    int mx = ptr->data;    
    while(ptr != NULL){
        if(mx < ptr->data)
            mx = ptr->data;
        ptr = ptr->next;
    }    
    return mx;
}
int main(){
    //assume linked list is given.
    cout << findMax(struct node * start);
    return 0;
}  

I: What is full Binary Tree?

M: Got confused with Complete Binary Tree(CBT). I told them a binary tree which is left filled and then changed my answer to a binary tree having all the leaves at the same level. But, they told that a tree in which all internal nodes have 2 children.

Data Structures:

I: Determine a logic or code to determine if a tree if full binary tree or not?

M: We can make a recursive call to the left and right subtree and for each node check if both left and right child is not null. When both the children are null means the terminating condition is reached and it is a full binary tree. Then I wrote a pseudo code.

I: Can you determine the recurrence relation and determine the time complexity?

M: I got a bit confused and told O(logn) thinking of BST. Then they helped with an example and wrote the recurrence relation as

T(n) = 2 * T(n/2) + c

Then applied the master's theorem

a = 2, b = 2, k = 0, p = 0
O(n)

 I: If some relative order is given in an unsorted array, how many comparisons are required? He told I am just asking you for the challenge you can think and search after the interview.

M: I told about topological sort and can apply DFS. I also discussed Tournament tree and comparison should be required O(n). But he told you are in the right direction but in this short span, it will difficult to take in the full solution. Have a look after the interview.  

Database Systems:

I: Do you know Durability?

M: It is one of the ACID properties. It shows that data in the system remain persistent.

I: How you achieve it. Please be technical.

M: Through creating logs.

I: Do you know the types of logs?

M: I did study but could not recall the types.

I: Why you need and how you achieve durability, consistency, etc.?

M: Check over system failure, local error, disk failure, etc. Periodical checks can be performed.

I: Write a Relational algebra to determine the names of the employee working under the supervision of supervisor ‘Smith’?

M: Pi(names)(Sigma(E1.sid = E2.eid and E2.name = ‘Smith’)(E1xE2)). We could have also used joins.

I: In DBMS whose responsibility to determine the consistency?

M: It is the responsibility of the database system to check the consistency.

I: Who is responsible for Isolation? 

M: Database Manager so that interleaved execution can be omitted.

I: Any questions?

M: If selected how the labs will be allotted (AIDB, RISE labs)?

I: After selection, you will be asked your choice and depending on the professor. Any more question?

M: No. 

I: You can leave the meeting and thank you.

M: Thank you, sir.

 

 

 

abhi97.dutta posted in Interview Experience Jul 23, 2020
2,043 views
115

Subject of choice: Data Structures

Questions:

  1. What is a BST?
  2. How will you traverse it?
  3. What is topological sorting?
  4. Where can you observe topological sorting in real life?
  5. Which BST traversal algorithm will give you exact/close approximation to topological sort?
  6. How will you modify the traversal algorithm to approximate topological sort? ( Couldn’t ans this well)
  7. Suppose you have an acyclic graph and there are two nodes which do now have an edge between them does swapping the two nodes have an effect on correctness of topological ordering?

Programming: WAP to find max element in linked list. 

s1lv3rj1nx posted in Interview Experience Jul 23, 2020
2,024 views
116
My interview was initially scheduled for July 22, on July 21(my birthday too xD) in the morning I saw a missed call, and I called back and it was hod of CSE department and he was like we’ll conduct your interview today itself. He called 3-4 times, kept on postponing the time of interview, and finally, in the evening he was like well do your interview tomorrow(I was like gg, day wasted and I started playing csgo immediately xD). On July 22 in the morning at 8:45 he called and asked me to join the interview.

Subject chosen – COA

There were 6 people including the hod and he was like we’ll ask you programming first and then COA, I was like cool.(I am just an average guy in programming with less experience)

hod – Hello Nikhil tell about yourself

Me – Uhm .. my name is Nikhil, computer is my first love , my aim since I was 6 years old was to learn computer in such a way that I have to be able to build a computer from scratch (i.e) I want to learn A-Z of a computer. I come from a shitty undergrad college where I wasn't able to learn any computer science, but then I joined gate coaching in my 4-2 where the faculty was really nice and I was able to learn real computer science.

hod was smiling and asked me where did I attend my gate coaching and which city I live in.

Me – Hyderabad and ace academy sir.

Then my programming interview began.

Interviewer 1 - Given a sorted linked list, write a function that finds the correct place for the given value and places it there.

Me – In my mind I was so happy because I felt that it was an easy question, and wrote the code in a stretch, I missed a corner case which I immediately recognized and was about to write additional code for that he was like cool leave it.

Interviewer 1 – Now he was like write another function which takes an array as input and returns a sorted linked list which has the elements of that array, has to use insertion sort and also use the previously written function.

Me – Again I was happy because I kind of can write the basic sorting algorithms fine. So I started writing the code and did a small mistake which I corrected in a minute when they pointed it out and finally I wrote the code fine(which I wasn't expecting xD).

Interviewer 1 was like I’m done

Interviewer 2 – I’ll ask you questions from COA, but first open your program and then he was like you used a lot of pointers in it, can you tell me which addressing mode is used in your code.

Me – In array we use indexed addressing mode and was explaining how it works then Interviewer 2 got disconnected from the call.

hod – It seems like Interviewer 2 has a technical problem, in the meanwhile I’ll ask you something

Me – sure sir

hod – “ Let me guess, your father has done PhD in IISC Bangalore?”

Me – I was like what?? inside my head laughed a little and told him no sir he used to work in a bank and is retired now, but I want to do PhD definitely after my masters.

(well maybe because of the way I look, I kind of had a beard, long hair, and spectacles)

hod – “hahaha fine I was just asking”

Interviewer 2 came back and started asking me to explain all the types of addressing modes

 I did explain all types

In2 – Do you know how many different levels of cache are present?

Me – 2-3

In2 – why do we need 2-3?

Me – told him that smaller the cache faster the speed usually, as searching in bigger search space could be slower than searching in smaller search space and explained a bit more.

In2 – How do we search for a byte in let’s say L3 cache?

Me – Uhm.. I’ll come from the virtual address generated by the CPU, address is a string of bits, well use the bits which are assigned for cache block number as select lines in the Nx1 MUX where N is the number of cache blocks and the selected blocks tag bits are sent to a comparator and compared with the tag bits in the address.

In2 – Ok can you tell me roughly the sizes of each level

Me – l1 – 32 KB maybe, l2- 256 KB l3-2MB

In2 – Now why do you say searching in L3 is slower than searching in L1 when same MUX and comparator are used?

Me – I was like uhm ok to win the argument I could say that 256 x 1 MUX is faster 1024 x 1 MUX

In2 – he smiled and was like no that isn’t the reason anyways tell me different types of cache.

Me – You mean like TLB, etc?

In2 – No I mean direct mapped etc..

Me – Oh cool, yes sir basically there are 3 types direct mapped, fully associative and set associative.

In2 – Explain about fully associative

Me – Anything can be anywhere (he smiled), I continued and was like any main memory block can be present in any cache block and the tag bits are everything except the byte offset in the address.

In2 – suppose in a 4 way set associative mapping in set-0 block 0 is present, can any other block come into that set?

Me – I said yes sir any main memory block which is multiple of 4

In2 was like 4? then I immediately responded

Me – sorry sir, I assumed that the number of cache sets is also 4, lets say that number of cache sets is S, then any block which is multiple of S can be present in set – 0.

In2 – now let's say there are 2 blocks in set – 0, already one block is filled now when a new block comes what happens?

Me – as another block in the set is empty it goes there

In2 – Now another block came in then?

Me – It depends on which cache replacement policy you use, could be LRU or FCFS etc..

In2 – ok can you tell me different cache misses in different types of cache?

Me – You mean like misses analysis in different mappings?

In2 – yeah exactly

Me – In direct mapped cache conflict misses are the highest as the number of main memory blocks contending for a single cache block is the highest here, in set-associative it is less than direct mapping and in fully associative it is the least. Compulsory misses are the same everywhere and these are the only misses I could think off.

In2 – Yeah that's fine(was satisfied with my answer and was like I’m done)

hod – Ok Nikhil your interview is done, do you have any questions?

Me – Sir, if someone accepts an offer in coap and got selected for MS in madras is there any mechanism which detects that?

hod – what is coap?(I was like what??? in my head. I guess we both misheard each other here xD) mtech seats are independent of MS seats.

Me – ok cool ignore my question.

PS – This was one of the best interviews I had so far, and I really like the people from IIT madras as they asked days before in which subjects I’d liked to be interviewed.

I even attended for IIT Gandhinagar interview where the interviewer was like tell me your favourite subjects

Me – COA and OS sir

Interviewer – Okay I’ll ask graph theory. (yup he did that and my interview didn’t go that well.)

My gate score is 776 rank 335 cat – general.
NIKHIL MOLUGU posted in Interview Experience Jul 22, 2020
1,362 views
117
Gate Score : 744

Rank : 460
Round : 2
Project : SAFE
 

Interview was on Google meet. Only my camera was on and I could not see any professors. Only 1 professor interacted with me throughout the interview. Nothing too fancy just basic questions, I don’t know why.

Q1. Give your educational background details

Q2. Saw my resume and looked at projects listed. I had 2 years of work experience in sql, java and ETL as software developer.

Q3. Talk about all your significant projects. ( I talked about my projects at work and Btech project which was related to IOT)

Q4. Give information about fork() call. What things are common between parent and child process and what things are different.

Q5. What is transport layer. Talk about various Transport layer protocols.

Q6. Difference between virtual memory and physical memory.

Q7. Congestion control algorithms.

Q8. Different parts of virtual memory and why its needed.

Q9. Why you want to come in Research domain when already working for 2 years.

In the end I asked about various research opportunities available.

Total Duration : 20 mins (I answered everything quickly and finished off :P)

Verdict : Selected

Thanks and Good luck everyone :)
Shourabh Payal posted in Interview Experience Jul 22, 2020 edited Jul 29, 2020 by Shourabh Payal
1,633 views
118

22nd July 2020
 

It was an online interview on Google Meet, they called an hour before to get ready for the interview.There were about 5-6 people sitting in panel with only few with video on.

With formal greetings they started, concerning of my health they asked me if not comfortable please take rest.
 

Interviewer – Where are you from?
Me- Delhi Sir

Interviewer-Are you in final year or completed your graduation?
Me- Sir I have graduated in 2017

Interviewer- What have you done in last 2-3years?
Me- Explained all, and why I left my job.

Interviewer-So we have it in 2 rounds, first we will have programming and secondly we will ask questions on subject of your choice.Can you remind us which subject you choose?
Me- Algorithms Sir

*----Programming Test ------*
They shared Codeshare.io link where I can write a proper C code with proper syntax.

Question – Given a 2D matrix with elements 0’s & 1’s, WAP to check if the number of one’s in current row is greater than equal to the above row.
I asked to use paper and pen first which they allowed, and later I typed the code, but they asked to change the parameter of the function of there choice. Later I got confused and messed by the synatx of parameter. But overall the algo was fine and they had no issue with that.

*---- Algorithms Interview ------*

Interviewer2 – Are you comfortable with graph algorithms?
Me(Nervously)- Yes sir

Interviewer2- Do you know what is MST?
Me – (Explained)

Interviewer2- Which algo to use to find MST?
Me-  Kruskal’s and Prim’s Algo

Interviewer2- Modify this algorithm and find a unique MST
There was long conversation regarding this, but I surely messed up and wasn’t able to explain well.
Lastly Interviewer2 told we can have it efficiently by storing , try it offline you will get it.

Interviewer- We have time boundation, we are done from our side. You can ask anything regarding the course college or anything you want to ask.
Just asked about the class mode for upcoming session and the interview was over.
They individually asked to take care of health.

It was so smooth and friendly experience. 
Overall it was around 40-45mins of interview.

Sahil Lihas posted in Interview Experience Jul 22, 2020
1,273 views
119

I- Interviewer, M- Me

I- What are your favorite subjects?

M- Linear Algebra, Probability, DS/Algo.

I- Given a matrix $A^2$=0, what can you infer from this?

M- A is nilpotent matrix, eigen values are zero.

I- What about determinant of A?

M- $A^2$=0 =>$|A|^2$=0 =>2*|A|=0 =>|A|=0

I- What about $A^{-1}$?

M- won’t exist.

I- How do  you define inverse?

M- A matrix when multiplied by original matrix produces identity matrix is inverse.

I- Can you prove inverse won’t exist without using any of determinant things (I guess he didn’t wanted to hear things like |A|=0, so inverse won’t exist)

M- Sir assume $A^{-1}$ exists.

$A^2$=0

$A^{-1}$$A^2$=$A^{-1}$0

($A^{-1}$A)A=0

A=0

so even if assumed $A^{-1}$ exists in that case, A has to be null matrix but even the inverse of null matrix doesn’t exist because any matrix multiplied by null matrix produces null matrix always and never an identity matrix, so A can’t have inverse in all cases.

I- What’s volume of a n-dimensional cube?

M- couldn’t answer.

I- In 3D, suppose $0\leq x \leq 1$, $0\leq y \leq 1$, $0\leq z \leq 1$and $x \leq y \leq z$, what will be the volume enclosed by the set of points?

M- couldn’t answer.

I- Let’s simplify for understanding purpose, In 2D, suppose $0\leq x \leq 1$, $0\leq y \leq 1$ and $x \leq y$, how’ll the set of points look like?

M- Area of triangle with vertex as (0,0), (1,0), (1,1).

I- What’s it’s area?

M- ½

I- Now come back to the 3D problem I asked, how’ll the shape look like?

M- Tetrahedron.

I- How will you approach to find the volume?

M- will use calculus and find a small enclosed volume then integrate over it.

I- Obviously calculus can be used but we’re talking about linear algebra, so tell me something in that regard?

M- still thinking so then he moved to the next question.

I- Suppose we’ve set of functions with domain {1….m} and range {1….n} (considering only integers in the intervals), suppose you’ve two functions f(x) and g(x), what is the expected number of values in domain for which f(x)=g(x)?

M- thinking….(interviewer starting to simplify)

I- Tell me the probability of f(x) (or g(x)) taking any one value from range, more precisely probability that f(x)=1?

M- 1/n

I- So probability that f(1)=g(1)=1?

M- 1/$n^2$

( can think of it as prob{f(1)=1&&g(1)=1}= prob{f(1)=1}*prob{g(1)=1}     ::Since f(x) and g(x) are independent.

                                                               = (1/n)*(1/n)= 1/$n^2$

I- Probability that f(1)=g(1)?

M- $\sum_{x=1}^{n}prob(f(1)=g(1)=x)=\sum_{x=1}^{n}1/n^2=n/n^2=1/n$

I- So now what’s the expected number of values where f(x)=g(x)?

M- m/n

I- How did you do?

M- Told them approximately the below thing but got confused later…

Expected Value= $\sum_{x=1}^{m}prob(f(x)=g(x))$= $\sum_{x=1}^{m}(1/n)=m/n$

Now comes the Algo Question...

I- You’ve an unsorted array of ‘n’ elements, minimum number of comparisons to find the second minimum element?

M- 2(n-1)

I- Are you sure, I can tell you that there is much more smaller value possible, let me give you an hint, consider ‘n’ teams playing against each other, how’ll you find the winner and the second winner?

M- We’ll first compare pairs of elements and choose the minimum and then compare the next set of minimum and so on until we find the last minimum element.

Number of comparisons = $\frac{n}{2}+\frac{n}{4}+\frac{n}{8}.........+\frac{n}{n}$

                                       = n-$\frac{1}{2}$

(did wrong calculation during the interview.)

I- How’ll you find the next minimum?

M- The next minimum would be the element that was last compared with the minimum element.

I- Consider the sorted array 1,2,3,4,5,6,7,8 what would you say now?

M- Yes, sir it won’t work that way.

I- Try to relate with the analogy of the teams playing matches?

M- The second minimum would’ve definitely lost against the first minimum at some point, so we can keep track of the entire path for the winner starting from first comparison to last and can find the second minimum in this path itself.

(Interviewers weren’t much satisfied it seemed, I guess they were hinting towards the tournament tree algo which I didn’t remembered that time.)

I- Why did you moved from Mechanical to CSE stream after first year?

M- Sir, I started to develop quite a bit of interest in coding in my 2nd sem and seniors and everyone used to say about the job scopes and ever growing opportunities in CS. So all these biased my mind with entering into CS.

I- Are you satisfied with your decision about jobs and all?

M- Sure sir, but recently I’ve started to develop more interests in research than jobs, in fact I didn’t go to placements in my college and prepared for entrance exams instead.

I- Why so much interest in research?

M- It came out of my research internship at ISI Kolkata last year, I did comparative analysis of corporate jobs and research life and found the later to be more exciting and learning new and creative things everyday on the way while corporate job seems to me like doing more or less the same thing everyday.

I- What all entrance exams you gave?

M- TIFR, GATE and JEST.

I- You can leave now, we’ll contact you later if something required.

(P.S.:- It might be possible that my answers written to above questions are wrong at many places, but the questions are very close to what I could remember. Overall TIFR being very good at Theoretical Computer Science research seemed to be much more focused on mathematics at depth. At TIFR, CS is only there at Mumbai Campus as of now.)

Shivct1782 posted in Interview Experience Jul 21, 2020 edited Jul 22, 2020 by Shivct1782
2,160 views
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There were 2 rounds both of which was conducted on Google Meet platform. Initially document verification was done online and then we were alloted to different Panel. There were 3 panels in round 1. The panel which I got consisted of 3 professors. They were Prof. Manish Singh(P1), Prof. Srijith P.K.(P2), and Prof. Maunendra Dasekar(P3).
Round 1 was of 10-15 mins. Only 2 of the 3 professors asked question to me.
P1 - In which dept are u pursuing your B.Tech. Then he asked of I knew the concept of random variables.
Me - Yes Sir
P1 - He shared a google docs link in the chat window and there one question was given. It was:-
X is a random variable which can take values 0,1,2. Given E(X)=1.2. Find the maximum value of E(X^2)
Me - I had to type out the solution and explain each and every line which I have written and how was I approaching the problem. In the end I was able to answer it.
P1:- Are u comfortable with DS and Algorithm.
Me - Yes sir.
P1:- How can we find the kth min from an array of n numbers.
Me - We can sort the array and get the value of kth index.
P1 - Time complexity of the code
Me - O(nlgn)
P1 - any better solution
Me - After thinking for a while i said we can use the concept of partition in quick sort.
P1 - Time complexity
Me - I analysed and got something like O(n^2). (But after the exam I searched and on geeksforgeeks site it was written this approch take O(n) time if implemented.)
P1 - Is there any other way as well which is better.
Me - I could not think of any better way. (There is one more approach using heap which is better).
P3 - Gave a list of numbers in the docs and asked me to find the median of the list of numbers given.
Me - Gave the answer and discussed the two formula for even no. of element case and odd no. of element case in the list.
Round 1 was over and we were said that if selected we would be sent email for 2nd round which would take place around 3pm. I received an email stating I was selected for the round 2 interview.
Round 2 there were 2 panel named panel 4 and panel 5. I was alloted to panel 4 where there were 4 professors namely Prof. Abhinav Kumar(P1), Prof. Vineeth N Balasubramanian(P2), Prof. SaiDhiraj Amuru(P3), and one more professor(P4) whose name I do not remember. Only 2 out of the 4 prof. asked question to me.  Round 2 lasted for 20-25 mins.
P1 - Introduce yourself. And why do u want to pursue M. Tech.
Me - Answered
P1 - Are u comfortable with probability.
Me - Yes Sir.
P1 - Do u know about gaussian random variable.
Me - No sir.
P1 - What random variables do u know.
Me - Binomial, Poisson, Uniform.
P1 - One basic question on conditional probability related to bags and balls without replacement.
Me - Answered that question.
P1 - You said u knew Uniform Random variable. Then given X is a uniform random variable from 0-2 and Y is a uniform Random variable from 1-3. Z ks another random variable which is defined as Z=X+Y. What is the PDF for Z and the graph using which it is represented.
Me - Z will be defined from 0-3 and the graph will be parallel to X axis from 0-3.
P2 - What have u studied in ML like which concept in ML would u be liked u asked about.
Me - Regression.
P2- Do u know Logistic regression.
Me - Not so much clear with the concepts.
P2 - Okay no problem. Do u know linear regression.
Me - Yes sir
P2 - Then tell me which concept we should follow if we want our regression line to be a curve instead to a straight line
Me - Multiple Linear Regression.
P2 - Any other algorithm which u would be liked to ask question about.
Me - Knn classifier
P2 gave me one situation and asked me what should be the value of k bigger, smaller or in between the total range of data.
Answered it.
P2 - Do u know about basis of a vector.
Me - No sir
And the interview was over and then the next day we were sent a list of projects in which we have to fill in our preferences for the project.
For the future aspirants I would recommend everyone to go through probability and linear algebra(especially vectors part) thoroughly and also some basic concept of ML algorithms which u can get by doing some courses online.
vineet2609 posted in Interview Experience Jul 21, 2020
3,822 views