tech-interview-handbook/preparing/cheatsheet.md

Interview Cheatsheet

This is a straight-to-the-point, distilled list of technical interview Do's and Don'ts, mainly for algorithmic interviews. Some of these may apply to only phone screens or whiteboard interviews, but most will apply to both. I revise this list before each of my interviews to remind myself of them and eventually internalized all of them to the point I do not have to rely on it anymore.

For a detailed walkthrough of interview preparation, refer to the "Preparing for a Coding Interview" section.

Legend: ✅ = Do, ❌ = Don't, ⚠️ = Situational

1. Before Interview

	Things
✅	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.
✅	Request for the option to interview over Hangouts/Skype instead of a phone call; it is easier to send links or text across.
✅	Decide on and be familiar with a programming language.
✅	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

	Things
✅	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.
❌	Spend too long introducing yourself. The more time you spend talking the less time you have to code.

3. Upon Getting the Question

	Things
✅	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 have seen before and how they were solved. Check out the tips in this section.
❌	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

	Things
✅	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.
❌	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

	Things
✅	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.
❌	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

	Things
✅	Ask questions. More importantly, ask good and engaging questions that are tailored to the company! Pick some questions from this list.
✅	Thank the interviewer.
⚠️	Ask about your interview performance. It can get awkward.
❌	End the interview without asking any questions.

7. Post Interview

	Things
✅	Record the interview questions and answers down as these can be useful for future reference.
⚠️	Send a follow up email to your interviewer(s) thanking them for their time and the opportunity to interview with them.