The Nightmare of Algorithm Interviews

A current widespread customized within the excessive know-how business is the “coding interview” the place candidates usually stand in entrance of a white board for 3 or extra hours answering questions on information buildings and algorithms usually taught in college-level pc science (CS) applications: sorting algorithms, looking algorithms, estimating the Large O order of the algorithm, implementing linked lists, timber, and hash tables.

The coding interview has turn into so frequent and pervasive that it has spawned a cottage business of books, programs, and coaches, most notably Gayle Laakmann McDowell’s Cracking the Coding Interview (now in its sixth version) recognized amongst cognoscenti by the acronym CTCI. Rivals embody Programming Interviews Uncovered: Secrets and techniques to Touchdown Your Subsequent Job (third version) by John Mongan, Coding Interview Questions by Narasimha Karumanchi, and dozens extra.

The coding interview has come underneath growing fireplace not too long ago with many essential weblog posts and a high-profile essential tweet by Ruby-on-Rails Creator David Heinemeier Hannson.

Whats up, my identify is David. I might fail to write down bubble type on a whiteboard. I look code up on the web on a regular basis. I don’t do riddles.

The Downside with Algorithm Interviews

As somebody who researches and develops algorithms with a excessive mathematical content material professionally I can say that these algorithm interviews don’t typically check expertise utilized in skilled algorithm growth not to mention many frequent software program growth duties akin to consumer interface growth, most websites, and most database software program growth.

Knowledge buildings akin to linked lists, timber, and hash tables are solved issues in pc science. Sorting and looking algorithms are additionally largely solved issues in pc science. The mantra in software program growth is code reuse, broadly used as a pretext for rewriting and reinventing working code written by different builders. Your code is just not maintainable (reusable), therefore I need to refactor it (rewrite it from scratch) relatively than reuse it.

Nonetheless, for these of us who truly follow code reuse, many libraries and instance supply code snippets exist for all of those information buildings and algorithms. Many of those may be discovered, if wanted, by utilizing Google or different search engines like google and yahoo. Extra to the purpose, the C++ Customary Template Library (STL), for instance, comprises templates implementing practically all of those.

The algorithm interviews thus are inclined to discriminate towards skilled builders who know what they’re doing and are long gone CS 101 or CS 201. They have an inclination much more to discriminate towards “self-taught” builders who might by no means have taken CS 101 or CS 201. The 2015 Stack Overflow Developer Survey discovered that forty-eight p.c of respondents didn’t have a CS diploma and 41.8 p.c described themselves as “self-taught.”

So known as self-taught software program builders are usually folks with non-CS STEM (Science, Expertise, Engineering, and Arithmetic) levels who realized software program growth by doing in these non-CS fields, a few of which akin to Physics have been utilizing computer systems and growing leading edge software program and algorithms earlier than CS even existed as a level. These self-taught software program builders who originate outdoors of a STEM area or lack a university diploma in all probability have a tendency on common to be at an excellent higher drawback.

Cracking the Coding Interview

To make sure, skilled software program builders with free time can get Cracking the Coding Interview or comparable texts and spend months training these non-representative algorithm issues. That’s precisely what many do.

About two years in the past, I assisted a pal and colleague with reworking from software program growth within the rareified world of Excessive Power Physics to what’s now being known as “information science.” After all, he had all of the requisite and usually exhausting to search out expertise. I had nevertheless to suggest that he get Cracking the Coding Interview and follow for a number of months. We additionally arrange a number of mock interview classes the place I bombarded him with the arcane algorithm and mind teaser questions that at present dominate the interview course of.

Not surprisingly, he did discover a good job after a number of months of trying and leaping by way of these weird hurdles. However, training these algorithm questions is time consuming, tedious, and a major hardship for these skilled scientists and engineers with households and different post-college obligations. It additionally takes away from time spent studying or training expertise truly used on the job.

The Downside with Job Interviews

In my expertise, job interviews of any kind will not be very dependable — for both the employer or the potential worker. Job interviews are a high-stakes check or examination the place each the potential employer and worker have a robust incentive to place their finest face ahead and keep away from potential downside areas. Many books like Cracking the Coding Interview, programs, coaches and consultants, and different sources exist for each employers and workers to be taught to current themselves nicely in a brief encounter that’s typically not consultant of the particular work and work surroundings.

There’s in all probability a weak constructive correlation between the impression fashioned in a job interview and what is going to truly occur, however it’s weak. There are numerous circumstances the place the job interview appears nice and the job is a horrible match. Certainly, there are a good variety of circumstances the place the job bears no resemblance to the job seemingly described within the job interview.

Fashionable algorithm interviews focus virtually solely on non-representative questions on technical expertise, largely avoiding discussions of what the job is, what the potential worker desires to do, what the potential worker has finished up to now, and different related “sensitive feely” points. Whereas a extra rounded interview course of would in all probability be more practical and considerably higher correlated with outcomes, such interviews have been frequent within the 1990’s and early 00’s and nonetheless had a excessive failure fee for each employers and workers.

Imperfect Options

Whereas portfolios of software program with instance code can reveal particular experience, it may be troublesome to confirm that the potential worker truly developed the code. Many full time workers and contractors can not construct up a consultant portfolio to indicate potential employers due to secrecy and confidentiality necessities. Apple, to present a infamous instance, is extraordinarily secretive. Though an excessive instance, it’s hardly distinctive amongst employers.

A trial consulting venture (paid) lasting a couple of weeks to some months might be extra dependable than a easy job interview, and lots of have steered these trial tasks as a doable answer to hiring difficulties. Nonetheless, even a trial venture is just not an ideal check for a lot of points. Some issues take longer to manifest than a couple of months. It’s nonetheless doable for a trial venture to be non-representative of the majority of the work, beginning after the trial venture is accomplished. Typically, a traditional job interview precedes a trial venture.

Trial tasks are nice for consultants with good funds and a great marketplace for their expertise, however clearly don’t work so nicely for full time workers, for instance with households that want assist and a focus.


The present CS 101/ CS 201 algorithm interviews that spend a lot of the interview on technical questions on information buildings and algorithms akin to linked lists and sorting algorithms will not be a great check both for common software program growth and even for {most professional} algorithm growth. Skilled algorithm builders usually reuse code or libraries with these information buildings and algorithms relatively than reinvent them. The broadly used C++ Customary Template Library (STL), for instance, consists of most of those. Many superior algorithms akin to video compression, speech recognition, neural networks, and lots of others actually make little or no use of those textbook algorithms.

Concerning the Writer

John F. McGowan, Ph.D. solves issues utilizing arithmetic and mathematical software program, together with growing gesture recognition for contact gadgets, video compression and speech recognition applied sciences. He has intensive expertise growing software program in C, C++, MATLAB, Python, Visible Fundamental and lots of different programming languages. He has been a Visiting Scholar at HP Labs growing pc imaginative and prescient algorithms and software program for cellular gadgets. He has labored as a contractor at NASA Ames Analysis Heart concerned within the analysis and growth of picture and video processing algorithms and know-how. He has printed articles on the origin and evolution of life, the exploration of Mars (anticipating the invention of methane on Mars), and low-cost entry to house. He has additionally labored for numerous startup firms and Apple.  He has a Ph.D. in physics from the College of Illinois at Urbana-Champaign and a B.S. in physics from the California Institute of Expertise (Caltech).  He may be reached at jmcgowan11 AT earthlink.web