I had the technical interview yesterday, which I thought went very well (but ended up in Match Not Ideal). Of all the questions asked, there were only three for which I did not have immediate correct (and detailed) answers. These questions were:
- Is the system y[n]=x[n]*x[n-1] time invariant?
- How do you see the contents of a .mat file without loading it into the workspace?
- How do you open a .m file from the command line?
Other than that it was standard stuff that's been listed here:
- Linear algebra concepts (rank, inverse, singular matrix, eigenvectors, null space)
- Find the rank of a 3x3 matrix (it was full rank by inspection)
- Find the inverse of a 2x2 Matrix
- Find the eigenvalues of a 2x2 matrix
- Calculus concepts (what is a derivative, integral, how are they related (FTC), ODE vs PDE)
- Integrate f(x)*g(x) where f(x)=x and g(x)=cos(x) (int by parts)
- Solve the ODE dy/dx = cos(x)/(2y) with y(0) = 1 -- solution y(x) = sqrt(sin(x)+1)
- C pointer and header questions
- const int a = 100; vs #define a 100;
- ++i vs. i++
- Nyquist sampling theorem
- required sampling frequency for cos(2*pi*250t)
- convolution vs. cross-correlation
- FIR vs IIR
- What is Fourier Transform?
- relationship between Z and DTFT
- is y[n]=x[n]*x[n-1] linear or time invariant?
- is y[n] = x[n^2] linear or time invariant?
- is H(z) = (2z^2 + 3z)/(z^2 + 2.5z + 1) stable?
- HDD vs RAM storage
- MATLAB plotting (two plots on one axis, plotyy(), subplot(), 'ro' option)
- concatenate strings
- peek inside of a .mat file
- generate vector of integers between 1 and n that are divisible by 3 (3:3:n)
- find the indices of the values in a vector that are divisible by 3 ( find( mod(x,3)==0)) )
- addpath()
- startup.m, how to set your working directory on startup
There were some other discussion questions, but nothing that is not listed here. As so many others have said, they clearly have some sort of question bank which they use repeatedly, and every question I was asked is listed in some form somewhere in these Glassdoor reviews. The interview questions are not hard, you just really have to be on the top of your game.
The rejection came as a surprise since I felt the interview went so well. It may just be that since the interview questions are all available online, they have the luxury of expecting you to answer every one correctly.
It's disappointing, since this would have been a fun place to work, but oh well. They don't pay enough, anyways (according to Glassdoor).
