# IISC CDS Interview Experience M.Tech(Research)

#### Bysoubhikbaral4

Jun 18, 2021

Here in this post we will discuss the overall IISC  CDS Interview Experience M. Tech(Research), questions asked in IISC CDS Interview  M. Tech and will provide some points on how you can clear  IISC CDS Interview  M.Tech(Research)  .

M. Tech cut off for these  changes every year for 2021 it low.  Unlike 2020 where cut off was an astonishingly high 845 GATE score for written test, this year the cut-off was a generous 700.

## IISC CDS Interview Experience, 2021

The  IISC CDS Interview  was divided into 2 phases:

• Written test
• Interview

17th May,2021:Interview:

The interview was conducted over Microsoft Teams. There were 4 professors in the call. Here is my interview (Ix=interviewer x):

I1:Read out my application form details like GATE score, B.E degree and Labs preferences.

Me:Confirmed

I1:What topics have you come prepared for ?

Me:Sir, linear algebra, probability,DSA and image processing basics.

I1:Starting with linear algebra.Can 2 matrices with different elements have same Eigen values?

Me:(after thinking for a moment)Yes sir,

I1:Can you give me an example?

Me: Gave example by keeping major diagonal elements same and using favourable minor diagonal elements, sometimes making Minor diagonal product zero and sometimes making one of the elements as 1.

I1:That is a pretty good example. This is a property of matrix. We write it as A=PBP^(-1).

Me:Oh yes. Isn’t this condition for diagonalizable matrices, sir?

I1:Yes, good observation.Now, can you prove that the two matrices A and PBP^(-1) have the same eigen values?

Me:Asked permission for using pen and paper and started thing along the equation A.X=lambda.X

After few minutes I was able to prove this and showed the solution on camera.

I1:(quite impressed)That is a really good proof. I2 now you can ask him questions.

I2:Are you comfortable with probability?

Me:Yes sir.

I2:Ok, suppose you are in a class of 30 students,what is the probability of having a birthday common with atleast 1 student in the class?

Me:Again used pen and paper. Thought in terms of discrete random variables.Say X represents number of students with whom I have a birthday in common.So basically I need to find P(X>=1) which is same as 1-P(X=0).

P(X=0)=(364/365)^29

So P(X>=1)=1-(364/365)^29.

I was also narrating my steps to I2 while solving.So I gave answer like this.

Me:Sir its a difficult calculation but would be close to 0.99.(Realized my mistake immediately and corrected)Sir actually 364/365^29 is close to 0.99, so probability would be something like 0.01 .

I2:Ok.So now suppose we have 400 students instead of 30.Would the probability increase or decrease?

Me:(A bit confused)Sir i think it would decrease.

I2:Are you sure?

Me:(Realized)No sir, actually since the number of students have increased, there is higher chance of having a common birthday and also 364/365^399 would yield a smaller value so 1-364/365^399 would have a larger value.

I2:Ok good. I3,would you like to ask some programming question(probably because my B.E was in printing XD).

I3:Yes.So can you write a program to find largest and second largest numbers in a given matrix.

Me:Yes sir.First I wrote a code finding largest in one pass and second largest in another pass and narrated the logic to I3.

I3:Ok that’s fine,can you optimize it, like try to do this in one pass.

Me:Did that.And showed the psuedo code on camera.

I3:Ok good.I4 do you have any questions?

I4:No I am fine.

I3:Ok your interview is over.We will now disconnect the call.

Me:Thank you sir.

My interview lasted only about 18 mins including introductions and salutations, which was relatively short,probably because I didn’t struggle much with any of the questions(not boasting).Overall, interview was great and it felt great to be interviewed by the best minds from one of the best research universities in the world. The professors were very friendly and as far as I felt, will always guide you through if you are stuck with some question.I would definitely recommend Gilbert Strang’s MIT OCW lectures on linear algebra to be thorough with theoretical understanding of the same. First 15 lectures should suffice.

26th May,2021:The provisional shortlist was released and my application number was on the list.I was really happy but still had some fears since there is always some chance that you may not make it to the final list although such chances are less if your interview went quite well like mine.

10th June,2021:Received offer letter in mail at 7:09PM

## Important Question for IISC CDS Interview

1. All the elements of a NxN matrix are 1. Can you guess at least one eigen value, quickly? Give reason in support of your answer.
2. I is an identity matrix of size NxN. U is a column vector of size Nx1. It is given, UTU≠OUTU≠O and UUTUUT is of size NxN. The following equation holds: [I−α[UUT]]U=−U[I−α[UUT]]U=−U where αα is a scalar. Find the value of scalar αα and also show the derivation.
3. Write an efficient algorithm to find out the multiplication of a Diagonal Matrix and an Anti-diagonal matrix of size NxN.

Programming Questions  for IISC CDS Interview [5+10=15]:

1. Check if the input array is in strictly non-decreasing order or not. [5 Marks]
2. The input sample Matrix M is of size n x n. Given, Filter Matrix W is of size m x m. Perform Convolution and find out the output matrix C of size (n-2) x (n-2). [10 Marks]

Above we discussed IISC CDS Interview Experience   and IISC CDS Interview Experience .Hope this give a overall idea of IISC CDS Interview Experience Process. If you liked it, do check your Interview Question Sections for more Interview Questions of Differnt Product and Sercive based company.