tech-interview-handbook/contents/cheatsheet.md

---
id: cheatsheet
title: 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.

## The Process

#### 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](../non-technical/behavioral.md) in an interview. |
| ✅ | Prepare some [questions to ask](../non-technical/questions-to-ask.md) 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](../algorithms) 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](../non-technical/questions-to-ask.md). |
| ✅ | 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. |