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Coding Interview University

Table of Contents

---------------- Everything below this point is optional ----------------

Additional Resources

How to use it

Everything below is an outline, and you should tackle the items in order from top to bottom.

Interview Process & General Interview Prep

Book List

This is a shorter list than what I used. This is abbreviated to save you time.

Interview Prep Books

Language Specific

Python

Before you Get Started

This list grew over many months, and yes, it kind of got out of hand.

Here are some mistakes I made so you'll have a better experience.

1. You Won't Remember it All

2. Use Flashcards

Make your own for free:

3. Start doing coding interview questions while you're learning data structures and algorithms,

You need to apply what you're learning to solving problems, or you'll forget. I made this mistake. Once you've learned a topic, and feel comfortable with it, like linked lists, open one of the coding interview books and do a couple of questions regarding linked lists. Then move on to the next learning topic. Then later, go back and do another linked list problem, or recursion problem, or whatever. But keep doing problems while you're learning. You're not being hired for knowledge, but how you apply the knowledge. There are several books and sites I recommend. See here for more: Coding Question Practice

4. Review, review, review

I keep a set of cheat sheets on ASCII, OSI stack, Big-O notations, and more. I study them when I have some spare time.

Take a break from programming problems for a half hour and go through your flashcards.

5. Focus

There are a lot of distractions that can take up valuable time. Focus and concentration are hard. Turn on some music without lyrics and you'll be able to focus pretty well.

  • Plan SQL exercises

The Daily Plan

Some subjects take one day, and some will take multiple days. Some are just learning with nothing to implement.

Each day I take one subject from the list below, watch videos about that subject, and write an implementation in:

  • Python - using built-in types (to keep practicing Python)
  • and write tests to ensure I'm doing it right, sometimes just using simple assert() statements

Why code in all of these?

  • Practice, practice, practice, until I'm sick of it, and can do it with no problem (some have many edge cases and bookkeeping details to remember)
  • Work within the raw constraints (allocating/freeing memory without help of garbage collection (except Python or Java))
  • Make use of built-in types so I have experience using the built-in tools for real-world use (not going to write my own linked list implementation in production)

You can see my code here:

You don't need to memorize the guts of every algorithm.

Write code on a whiteboard or paper, not a computer. Test with some sample inputs. Then test it out on a computer.

Prerequisite Knowledge

(E: 5 hrs) Algorithmic complexity / Big-O / Asymptotic analysis

Data Structures

More Knowledge

Trees

(E: 30 hrs) Sorting

As a summary, here is a visual representation of 15 sorting algorithms. If you need more detail on this subject, see "Sorting" section in Additional Detail on Some Subjects

(E: 30 hrs) Graphs

Graphs can be used to represent many problems in computer science, so this section is long, like trees and sorting were.

Even More Knowledge

(E: 20 hrs) System Design, Scalability, Data Handling

You can expect system design questions if you have 4+ years of experience.

Final Review

This section will have shorter videos that you can watch pretty quickly to review most of the important concepts.
It's nice if you want a refresher often.

Coding Question Practice

Now that you know all the computer science topics above, it's time to practice answering coding problems.

Coding question practice is not about memorizing answers to programming problems.

Why you need to practice doing programming problems:

  • problem recognition, and where the right data structures and algorithms fit in
  • gathering requirements for the problem
  • talking your way through the problem like you will in the interview
  • coding on a whiteboard or paper, not a computer
  • coming up with time and space complexity for your solutions
  • testing your solutions

There is a great intro for methodical, communicative problem solving in an interview. You'll get this from the programming interview books, too, but I found this outstanding: Algorithm design canvas

No whiteboard at home? That makes sense. I'm a weirdo and have a big whiteboard. Instead of a whiteboard, pick up a large drawing pad from an art store. You can sit on the couch and practice. This is my "sofa whiteboard". I added the pen in the photo for scale. If you use a pen, you'll wish you could erase. Gets messy quick. I use a pencil and eraser.

my sofa whiteboard

Supplemental:

Read and Do Programming Problems (in this order):

See Book List above

Coding exercises/challenges

Once you've learned your brains out, put those brains to work. Take coding challenges every day, as many as you can.

Coding Interview Question Videos:

Challenge sites:

Challenge repos:

Facebook Interview Questions till date

  1. Phone Screen:
  1. Coding Round 1:

https://leetcode.com/problems/insert-interval/ https://leetcode.com/problems/convert-a-number-to-hexadecimal/ https://leetcode.com/problems/rotate-array/ https://leetcode.com/problems/k-closest-points-to-origin/ https://leetcode.com/discuss/interview-question/124759/ https://leetcode.com/problems/product-of-array-except-self https://leetcode.com/problems/find-all-anagrams-in-a-string/ https://leetcode.com/problems/minimum-window-substring/ https://www.***.org/find-closest-element-binary-search-tree/ https://leetcode.com/problems/insert-delete-getrandom-o1/ https://leetcode.com/problems/fraction-to-recurring-decimal/ https://leetcode.com/problems/powx-n https://leetcode.com/problems/subarray-sum-equals-k https://leetcode.com/problems/best-time-to-buy-and-sell-stock https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iii https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iv https://leetcode.com/problems/add-and-search-word-data-structure-design https://leetcode.com/problems/sudoku-solver/ https://leetcode.com/discuss/interview-question/338948/Facebook-or-Onsite-or-Schedule-of-Tasks https://leetcode.com/problems/binary-tree-maximum-path-sum https://leetcode.com/problems/maximum-subarray https://leetcode.com/problems/move-zeroes https://leetcode.com/problems/valid-number https://leetcode.com/problems/first-bad-version/

  1. Coding Round 2:

https://leetcode.com/problems/valid-number/ You have an API to check if is it possible to move left, right, up, down and one more method to check if current position is the last one. Find the shortest way to the last position. You don't have any data structure - only API. https://leetcode.com/problems/serialize-and-deserialize-binary-tree/ https://leetcode.com/problems/group-shifted-strings/ https://leetcode.com/problems/task-scheduler/ Calculate tax if Salary and Tax Brackets are given as list in the form [ [10000, 0.3],[20000, 0.2], [30000, 0.1], [null, .1]] null being rest of the salary Is there a way to reach (0,0) from a mXn matrix to (m-1,n-1) position and give the path. https://leetcode.com/problems/simplify-path/ n-ary Tree with each node having a boolean flag. Traverse all the nodes with only boolean flag = True. Return the total distance traveled from root to all those nodes. https://leetcode.com/problems/product-of-array-except-self/ https://leetcode.com/discuss/interview-question/432086/Facebook-or-Phone-Screen-or-Task-Scheduler/394783 https://leetcode.com/problems/find-all-anagrams-in-a-string https://leetcode.com/problems/is-graph-bipartite https://leetcode.com/problems/merge-sorted-array https://leetcode.com/problems/maximum-subarray https://leetcode.com/problems/serialize-and-deserialize-binary-tree https://leetcode.com/problems/remove-invalid-parentheses/ https://leetcode.com/problems/subarray-sum-equals-k/ https://leetcode.com/problems/binary-tree-level-order-traversal/ https://leetcode.com/problems/longest-increasing-path-in-a-matrix/ https://leetcode.com/problems/custom-sort-string https://leetcode.com/problems/read-n-characters-given-read4 https://leetcode.com/problems/remove-invalid-parentheses https://leetcode.com/problems/palindrome-permutation https://leetcode.com/problems/max-consecutive-ones-iii https://leetcode.com/problems/range-sum-of-bst https://leetcode.com/problems/exclusive-time-of-functions https://leetcode.com/problems/search-in-rotated-sorted-array/ https://leetcode.com/problems/search-in-rotated-sorted-array-ii/

  1. Design:

Design Google search Some question related to caching and balancing. Not exactly the "design twitter" type of question, but expect to talk about different components, latency, throughput, consistency and availability. A remote server is not responding. Debug the issue. Needed to cover entire TCP/IP stack(fragmentation/icmp/etc) + machine metrics (vmstat,iostat,strace etc). Describe virtual memory in terms of demand paging. 2 machines are connected, suddenly 1 machine is responding slowly. Why ? We had a good discussion in which we discussed everything under the sun, from NFS being bad to Networking being wrong to Kernel running out of resources(buffer-cache/inodes/virtual memory). Interviewer was interested to know the commands that i would use (strace, lsof, readlink, cat /proc/pid etc). Copy some resource from N sources to M sinks. where N could be < 10 and M could be 10k/Millions etc. Design File Storage System. Like Dropbox, Google Drive Not any fancy one like design Twitter or Uber. More on scheduling service side and i designed using SQL appraoch. Discussed concuurency issues, Table schemas, composite keys etc. Design recommendation of celebrities to user on Instagram Design search for Twitter Design a Content publishing site with privacy restrictions. System Design of Uber. He liked my design. He was really nice guy, i felt he was interested in my success. Design a type ahead features for a website. We discussed various data structures, advantage /disadvantages. Lot of different cases, scenario to handle etc. Design instagram client side. Design a leetcode contest, leadership board system Design Instagram Design keyword search in FB Posts There are music providers like spotify, apple music etc. Design a service for these providers to display top 10 songs played by each user. Was aked to write ER tables and API's. Design a system like Hacker Rank for a programming contest and their ranking. 5. Behavioral:

Work experience, past projects, standard "tell me about a time" questions, hypothetical scenario questions

  • Usual stuff around things that I am proud of/ projects that I regret etc
    • Answers:
    • Proud of data stack
    • Not proud of last mile of catalog project
    • Proud of building team and placing strategic bets
  • Tell me about your current role
    • 70% coding + architecture + code review
    • 20% people management 1:1, interviewing, resources, networking
    • 10% project management JIRA
  • Tell me about a projects you are proud of
  • Tell Me About A Time When You Had To Give Someone Difficult Feedback. How Did You Handle It?(What kind of feedback you give ?)
    • Jonathan Data Analyst wanting to become data engineer
  • Tell me about a time when you had a conflict with a manage and how you resolved it
    • Async + Dynamo
    • Tradeoff + wins
  • What's the most difficult/challenging problem you have had to solve?
    • UEL in 2 weeks
  • Which environment is best to you to work ? *
  • Tell about best decision in your life from childhood ? Decision that changed your life
    • SnapTravel
  • On which topics you want improve? What are doing to impoving on that topics ? Did you try build project on that topics ?
    • E2E delivery of Data projects
    • Learn to be a good manager from my leaders

Once you're closer to the interview

Be thinking of for when the interview comes

Think of about 20 interview questions you'll get, along with the lines of the items below. Have 2-3 answers for each. Have a story, not just data, about something you accomplished.

  • Why do you want this job?
  • What's a tough problem you've solved?
  • Biggest challenges faced?
  • Best/worst designs seen?
  • Ideas for improving an existing product.
  • How do you work best, as an individual and as part of a team?
  • Which of your skills or experiences would be assets in the role and why?
  • What did you most enjoy at [job x / project y]?
  • What was the biggest challenge you faced at [job x / project y]?
  • What was the hardest bug you faced at [job x / project y]?
  • What did you learn at [job x / project y]?
  • What would you have done better at [job x / project y]?

Have questions for the interviewer

Some of mine (I already may know answer to but want their opinion or team perspective):
  • How large is your team?
  • What does your dev cycle look like? Do you do waterfall/sprints/agile?
  • Are rushes to deadlines common? Or is there flexibility?
  • How are decisions made in your team?
  • How many meetings do you have per week?
  • Do you feel your work environment helps you concentrate?
  • What are you working on?
  • What do you like about it?
  • What is the work life like?
  • How is work/life balance?

Once You've Got The Job

Congratulations!

Keep learning.

You're never really done.

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Everything below this point is optional.
By studying these, you'll get greater exposure to more CS concepts, and will be better prepared for
any software engineering job. You'll be a much more well-rounded software engineer.

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Additional Books

These are here so you can dive into a topic you find interesting.

  • The Unix Programming Environment

    • an oldie but a goodie

  • The Linux Command Line: A Complete Introduction

    • a modern option

  • TCP/IP Illustrated Series

  • Head First Design Patterns

    • a gentle introduction to design patterns

  • Design Patterns: Elements of Reusable Object-Oriente​d Software

    • aka the "Gang Of Four" book, or GOF
    • the canonical design patterns book

  • UNIX and Linux System Administration Handbook, 5th Edition

  • Algorithm Design Manual (Skiena)

    • As a review and problem recognition
    • The algorithm catalog portion is well beyond the scope of difficulty you'll get in an interview.
    • This book has 2 parts:
      • class textbook on data structures and algorithms
        • pros:
          • is a good review as any algorithms textbook would be
          • nice stories from his experiences solving problems in industry and academia
          • code examples in C
        • cons:
          • can be as dense or impenetrable as CLRS, and in some cases, CLRS may be a better alternative for some subjects
          • chapters 7, 8, 9 can be painful to try to follow, as some items are not explained well or require more brain than I have
          • don't get me wrong: I like Skiena, his teaching style, and mannerisms, but I may not be Stony Brook material.
      • algorithm catalog:
        • this is the real reason you buy this book.
        • about to get to this part. Will update here once I've made my way through it.
    • Can rent it on kindle
    • Answers:
    • Errata

  • Write Great Code: Volume 1: Understanding the Machine

    • The book was published in 2004, and is somewhat outdated, but it's a terrific resource for understanding a computer in brief.
    • The author invented HLA, so take mentions and examples in HLA with a grain of salt. Not widely used, but decent examples of what assembly looks like.
    • These chapters are worth the read to give you a nice foundation:
      • Chapter 2 - Numeric Representation
      • Chapter 3 - Binary Arithmetic and Bit Operations
      • Chapter 4 - Floating-Point Representation
      • Chapter 5 - Character Representation
      • Chapter 6 - Memory Organization and Access
      • Chapter 7 - Composite Data Types and Memory Objects
      • Chapter 9 - CPU Architecture
      • Chapter 10 - Instruction Set Architecture
      • Chapter 11 - Memory Architecture and Organization

  • Introduction to Algorithms

    • Important: Reading this book will only have limited value. This book is a great review of algorithms and data structures, but won't teach you how to write good code. You have to be able to code a decent solution efficiently.
    • aka CLR, sometimes CLRS, because Stein was late to the game

  • Computer Architecture, Sixth Edition: A Quantitative Approach

    • For a richer, more up-to-date (2017), but longer treatment

  • Programming Pearls

    • The first couple of chapters present clever solutions to programming problems (some very old using data tape) but that is just an intro. This a guidebook on program design and architecture.

Additional Learning

I added them to help you become a well-rounded software engineer, and to be aware of certain
technologies and algorithms, so you'll have a bigger toolbox.

Additional Detail on Some Subjects

I added these to reinforce some ideas already presented above, but didn't want to include them
above because it's just too much. It's easy to overdo it on a subject.
You want to get hired in this century, right?

Video Series

Sit back and enjoy. "Netflix and skill" :P

Computer Science Courses

Papers

LICENSE

CC-BY-SA-4.0