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Hackernoon logoThe Tech Interview Cheatsheet by@yangshun

The Tech Interview Cheatsheet

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@yangshunYangshun Tay

Inside one of Airbnb HQ’s amazing conference rooms

Straight-to-the-point list of technical interview Do’s and Don’ts

Technical interviews can be unnerving at times. It is one of those things where many people dislike but still have to go through. Fortunately, technical interviewing is a skill that one can improve at. I got better at them through tons of practice and mock interviewing. In the process of preparation, I have compiled a list of Do’s and Don’ts that I revise before each of my interviews to remind myself of them. Hopefully any potential interviewee can benefit from them!

The content for this post can be found in my Tech Interview Handbook repo on GitHub. Updates will be made there. Pull requests for suggestions and corrections are welcome!

1. Before the Interview

Do’s

  • Prepare pen, paper and earphones/headphones.
  • Find a quiet environment with good Internet connection.
  • Ensure webcam and audio are working. There were times I had to restart Chrome to get Hangouts to work again.
  • Decide on and be familiar with a programming language.
  • Request for the option to interview over Hangouts/Skype instead of a phone call; it is easier to send links or text across.
  • Familiarize yourself with the coding environment (CoderPad/CodePen). Set up the coding shortcuts, turn on autocompletion, tab spacing, etc.
  • Prepare answers to the frequently-asked questions in an interview.|
  • Prepare some questions to ask at the end of the interview.
  • Dress comfortably. Usually you do not need to wear smart clothes, casual should be fine. T-shirts and jeans are acceptable at most places.
  • Stay calm and composed.
  • Turn off the webcam if possible. Most remote interviews will not require video chat and leaving it on only serves as a distraction.

2. Introduction

Do’s

  • Introduce yourself in a few sentences under a minute or two.
  • Mention interesting points that are relevant to the role you are applying for.
  • Sound enthusiastic! Speak with a smile and you will naturally sound more engaging.

Don’ts

  • Spend too long introducing yourself. The more time you spend talk the less time you have to code.

3. Upon Getting the Question

Do’s

  • Repeat the question back at the interviewer.
  • Clarify any assumptions you made subconsciously. Many questions are under-specified on purpose. A tree-like diagram could very well be a graph that allows for cycles and a naive recursive solution would not work.
  • Clarify input format and range. Ask whether input can be assumed to be well-formed and non-null.
  • Work through a small example to ensure you understood the question.
  • Explain a high level approach even if it is a brute force one.
  • Improve upon the approach and optimize. Reduce duplicated work and cache repeated computations.
  • Think carefully, then state and explain the time and space complexity of your approaches.
  • If stuck, think about related problems you’ve seen before and how they were solved. Check out the tips in this section.

Don’ts

  • Ignore information given to you. Every piece is important.
  • Jump into coding straightaway.
  • Start coding without interviewer’s green light.
  • Appear too unsure about your approach or analysis.

4. During Coding

Do’s

  • Explain what you are coding/typing to the interviewer, what you are trying to achieve.
  • Practice good coding style. Clear variable names, consistent operator spacing, proper indentation, etc.
  • Type/write at a reasonable speed.
  • As much as possible, write actual compilable code, not pseudocode.
  • Write in a modular fashion. Extract out chunks of repeated code into functions.
  • Ask for permission to use trivial functions without having to implement them; saves you some time.
  • Use the hints given by the interviewer.
  • Demonstrate mastery of your chosen programming language.
  • Demonstrate technical knowledge in data structures and algorithms.
  • If you are cutting corners in your code, state that out loud to your interviewer and say what you would do in a non-interview setting (no time constraints). E.g., I would write a regex to parse this string rather than using split()which may not cover all cases.
  • Practice whiteboard space-management skills.
  • Reasonable defensive coding. Check for nulls, empty collections, etc. Can omit if input validity has been clarified with the interviewer.

Don’ts

  • Remain quiet the whole time.
  • Spend too much time writing comments.
  • Use extremely verbose variable names.
  • Copy and paste code without checking.
  • Interrupt your interviewer when they are talking. Usually if they speak, they are trying to give you hints or steer you in the right direction.
  • Write too big (takes up too much space) or too small (illegible) if on a whiteboard.

5. After Coding

Do’s

  • Scan through your code for mistakes as if it was your first time seeing code written by someone else.
  • Check for off-by-one errors.
  • Come up with more test cases. Try extreme test cases.
  • Step through your code with those test cases.
  • Look out for places where you can refactor.
  • Reiterate the time and space complexity of your code.
  • Explain trade-offs and how the code/approach can be improved if given more time.

Don’ts

  • Immediately announce that you are done coding. Do the above first!
  • Argue with the interviewer. They may be wrong but that is very unlikely given that they are familiar with the question.

6. Wrap Up

Do’s

  • Ask questions. More importantly, ask good and engaging questions that are tailored to the company! Pick some questions from this list.
  • Thank the interviewer.

Don’ts

  • End the interview without asking any questions.
  • Ask about your interview performance. It can get awkward.

Internalize the above and practice them during your interviews (or mock interviews) and you are sure to see a visible improvement in your technical interview performance. Good luck!

If you enjoyed this article, please don’t forget to clap👏 ! (Do you know that you can clap more than once? Try it and see for yourself!)

You can also follow me on GitHub and Twitter.

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