Coding Interview University

I originally created this as a short to-do list of study topics for becoming a software engineer, but it grew to the large list you see today. After going through this study plan, I got hired as a Software Development Engineer at Amazon! You probably won't have to study as much as I did. Anyway, everything you need is here.

I studied about 8-12 hours a day, for several months. This is my story: Why I studied full-time for 8 months for a Google interview

Please Note: You won't need to study as much as I did. I wasted a lot of time on things I didn't need to know. More info about that below. I'll help you get there without wasting your precious time.

The items listed here will prepare you well for a technical interview at just about any software company, including the giants: Amazon, Facebook, Google, and Microsoft.

Best of luck to you!

Translations:

Translations in progress:

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What is it?

This is my multi-month study plan for becoming a software engineer for a large company.

Required:

A little experience with coding (variables, loops, methods/functions, etc)
Patience
Time

Note this is a study plan for software engineering, not frontend engineering or fullstack development. There are really super roadmaps and coursework for those career paths elsewhere (see https://roadmap.sh/ for more info).

There is a lot to learn in a university Computer Science program, but only knowing about 75% is good enough for an interview, so that's what I cover here. For a complete CS self-taught program, the resources for my study plan have been included in Kamran Ahmed's Computer Science Roadmap: https://roadmap.sh/computer-science

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

Optional Extra Topics & Resources

Additional Books
System Design, Scalability, Data Handling (if you have 4+ years experience)
Additional Learning
- Compilers
- Emacs and vi(m)
- Unix command line tools
- Information theory
- Parity & Hamming Code
- Entropy
- Cryptography
- Compression
- Computer Security
- Garbage collection
- Parallel Programming
- Messaging, Serialization, and Queueing Systems
- A*
- Fast Fourier Transform
- Bloom Filter
- HyperLogLog
- Locality-Sensitive Hashing
- van Emde Boas Trees
- Augmented Data Structures
- Balanced search trees
  - AVL trees
  - Splay trees
  - Red/black trees
  - 2-3 search trees
  - 2-3-4 Trees (aka 2-4 trees)
  - N-ary (K-ary, M-ary) trees
  - B-Trees
- k-D Trees
- Skip lists
- Network Flows
- Disjoint Sets & Union Find
- Math for Fast Processing
- Treap
- Linear Programming
- Geometry, Convex hull
- Discrete math
Additional Detail on Some Subjects
Video Series
Computer Science Courses
Papers

Why use it?

If you want to work as a software engineer for a large company, these are the things you have to know.

If you missed out on getting a degree in computer science, like I did, this will catch you up and save four years of your life.

When I started this project, I didn't know a stack from a heap, didn't know Big-O anything, or anything about trees, or how to traverse a graph. If I had to code a sorting algorithm, I can tell ya it would have been terrible. Every data structure I had ever used was built into the language, and I didn't know how they worked under the hood at all. I never had to manage memory unless a process I was running would give an "out of memory" error, and then I'd have to find a workaround. I used a few multidimensional arrays in my life and thousands of associative arrays, but I never created data structures from scratch.

It's a long plan. It may take you months. If you are familiar with a lot of this already it will take you a lot less time.

How to use it

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

I'm using GitHub's special markdown flavor, including tasks lists to track progress.

More about GitHub-flavored markdown

If you don't want to use git

On this page, click the Code button near the top, then click "Download ZIP". Unzip the file and you can work with the text files.

If you're open in a code editor that understands markdown, you'll see everything formatted nicely.

If you're comfortable with git

Create a new branch so you can check items like this, just put an x in the brackets: [x]

Fork the GitHub repo: https://github.com/jwasham/coding-interview-university by clicking on the Fork button.

Clone to your local repo:

git clone https://github.com/<YOUR_GITHUB_USERNAME>/coding-interview-university.git
cd coding-interview-university
git remote add upstream https://github.com/jwasham/coding-interview-university.git
git remote set-url --push upstream DISABLE  # so that you don't push your personal progress back to the original repo

Mark all boxes with X after you completed your changes:

git commit -am "Marked personal progress"
git pull upstream main  # keep your fork up-to-date with changes from the original repo

git push # just pushes to your fork

Don't feel you aren't smart enough

Successful software engineers are smart, but many have an insecurity that they aren't smart enough.
Following videos may help you overcome this insecurity:
- The myth of the Genius Programmer
- It's Dangerous to Go Alone: Battling the Invisible Monsters in Tech

A Note About Video Resources

Some videos are available only by enrolling in a Coursera or EdX class. These are called MOOCs. Sometimes the classes are not in session so you have to wait a couple of months, so you have no access.

It would be great to replace the online course resources with free and always-available public sources, such as YouTube videos (preferably university lectures), so that you people can study these anytime, not just when a specific online course is in session.

Choose a Programming Language

You'll need to choose a programming language for the coding interviews you do, but you'll also need to find a language that you can use to study computer science concepts.

Preferably the language would be the same, so that you only need to be proficient in one.

For this Study Plan

When I did the study plan, I used 2 languages for most of it: C and Python

C: Very low level. Allows you to deal with pointers and memory allocation/deallocation, so you feel the data structures and algorithms in your bones. In higher level languages like Python or Java, these are hidden from you. In day to day work, that's terrific, but when you're learning how these low-level data structures are built, it's great to feel close to the metal.
- C is everywhere. You'll see examples in books, lectures, videos, everywhere while you're studying.
- The C Programming Language, 2nd Edition
  - This is a short book, but it will give you a great handle on the C language and if you practice it a little you'll quickly get proficient. Understanding C helps you understand how programs and memory work.
  - You don't need to go super deep in the book (or even finish it). Just get to where you're comfortable reading and writing in C.
  - Answers to questions in the book
Python: Modern and very expressive, I learned it because it's just super useful and also allows me to write less code in an interview.

This is my preference. You do what you like, of course.

You may not need it, but here are some sites for learning a new language:

For your Coding Interview

You can use a language you are comfortable in to do the coding part of the interview, but for large companies, these are solid choices:

C++
Java
Python

You could also use these, but read around first. There may be caveats:

JavaScript
Ruby

Here is an article I wrote about choosing a language for the interview: Pick One Language for the Coding Interview. This is the original article my post was based on: Choosing a Programming Language for Interviews

You need to be very comfortable in the language and be knowledgeable.

Books for Data Structures and Algorithms

This book will form your foundation for computer science.

Just choose one, in a language that you will be comfortable with. You'll be doing a lot of reading and coding.

C

Algorithms in C, Parts 1-5 (Bundle), 3rd Edition
- Fundamentals, Data Structures, Sorting, Searching, and Graph Algorithms

Python

Data Structures and Algorithms in Python
- by Goodrich, Tamassia, Goldwasser
- I loved this book. It covered everything and more.
- Pythonic code
- my glowing book report: https://startupnextdoor.com/book-report-data-structures-and-algorithms-in-python/

Java

Your choice:

Goodrich, Tamassia, Goldwasser
- Data Structures and Algorithms in Java
Sedgewick and Wayne:
- Algorithms
- Free Coursera course that covers the book (taught by the authors!):
  - Algorithms I
  - Algorithms II

C++

Your choice:

Goodrich, Tamassia, and Mount
- Data Structures and Algorithms in C++, 2nd Edition
Sedgewick and Wayne
- Algorithms in C++, Parts 1-4: Fundamentals, Data Structure, Sorting, Searching
- Algorithms in C++ Part 5: Graph Algorithms

Interview Prep Books

You don't need to buy a bunch of these. Honestly "Cracking the Coding Interview" is probably enough, but I bought more to give myself more practice. But I always do too much.

I bought both of these. They gave me plenty of practice.

Programming Interviews Exposed: Coding Your Way Through the Interview, 4th Edition
- Answers in C++ and Java
- This is a good warm-up for Cracking the Coding Interview
- Not too difficult. Most problems may be easier than what you'll see in an interview (from what I've read)
Cracking the Coding Interview, 6th Edition
- answers in Java

If you have tons of extra time:

Choose one:

Don't Make My Mistakes

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

Here are some mistakes I made so you'll have a better experience. And you'll save months of time.

1. You Won't Remember it All

I watched hours of videos and took copious notes, and months later there was much I didn't remember. I spent 3 days going through my notes and making flashcards, so I could review. I didn't need all of that knowledge.

Please, read so you won't make my mistakes:

Retaining Computer Science Knowledge.

2. Use Flashcards

To solve the problem, I made a little flashcards site where I could add flashcards of 2 types: general and code. Each card has different formatting. I made a mobile-first website, so I could review on my phone or tablet, wherever I am.

Make your own for free:

Flashcards site repo

I DON'T RECOMMEND using my flashcards. There are too many and most of them are trivia that you don't need.

But if you don't want to listen to me, here you go:

Keep in mind I went overboard and have cards covering everything from assembly language and Python trivia to machine learning and statistics. It's way too much for what's required.

Note on flashcards: The first time you recognize you know the answer, don't mark it as known. You have to see the same card and answer it several times correctly before you really know it. Repetition will put that knowledge deeper in your brain.

An alternative to using my flashcard site is Anki, which has been recommended to me numerous times. It uses a repetition system to help you remember. It's user-friendly, available on all platforms and has a cloud sync system. It costs $25 on iOS but is free on other platforms.

My flashcard database in Anki format: https://ankiweb.net/shared/info/25173560 (thanks @xiewenya).

Some students have mentioned formatting issues with white space that can be fixed by doing the following: open deck, edit card, click cards, select the "styling" radio button, add the member "white-space: pre;" to the card class.

3. Do Coding Interview Questions While You're Learning

THIS IS VERY IMPORTANT.

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 somewhat comfortable with it, for example, linked lists:

Open one of the coding interview books (or coding problem websites, listed below)
Do 2 or 3 questions regarding linked lists.
Move on to the next learning topic.
Later, go back and do another 2 or 3 linked list problems.
Do this with each new topic you learn.

Keep doing problems while you're learning all this stuff, not after.

You're not being hired for knowledge, but how you apply the knowledge.

There are many resources for this, listed below. Keep going.

4. 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.

What you won't see covered

These are prevalent technologies but not part of this study plan:

Javascript
HTML, CSS, and other front-end technologies
SQL

The Daily Plan

This course goes over a lot of subjects. Each will probably take you a few days, or maybe even a week or more. It depends on your schedule.

Each day, take the next subject in the list, watch some videos about that subject, and then write an implementation of that data structure or algorithm in the language you chose for this course.

You can see my code here:

You don't need to memorize every algorithm. You just need to be able to understand it enough to be able to write your own implementation.

Coding Question Practice

Why is this here? I'm not ready to interview.

Then go back and read this.

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 (see Big-O below)
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

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

If you don't have a whiteboard at home, 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 just for scale. If you use a pen, you'll wish you could erase. Gets messy quick. I use a pencil and eraser.

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

Coding Problems

Don't forget your key coding interview books here.

Solving Problems:

Coding Interview Question Videos:

IDeserve (88 videos)
Tushar Roy (5 playlists)
- Super for walkthroughs of problem solutions
Nick White - LeetCode Solutions (187 Videos)
- Good explanations of solution and the code
- You can watch several in a short time
FisherCoder - LeetCode Solutions

Challenge/Practice sites:

LeetCode
- My favorite coding problem site. It's worth the subscription money for the 1-2 months you'll likely be preparing.
- See Nick White and FisherCoder Videos above for code walk-throughs.
HackerRank
TopCoder
Codeforces
Codility
Geeks for Geeks
AlgoExpert
- Created by Google engineers, this is also an excellent resource to hone your skills.
Project Euler
- very math focused, and not really suited for coding interviews

Let's Get Started

Alright, enough talk, let's learn!

But don't forget to do coding problems from above while you learn!

Algorithmic complexity / Big-O / Asymptotic analysis

Nothing to implement here, you're just watching videos and taking notes! Yay!
There are a lot of videos here. Just watch enough until you understand it. You can always come back and review.
Don't worry if you don't understand all the math behind it.
You just need to understand how to express the complexity of an algorithm in terms of Big-O.
Harvard CS50 - Asymptotic Notation (video)
Big O Notations (general quick tutorial) (video)
Big O Notation (and Omega and Theta) - best mathematical explanation (video)
Skiena (video)
UC Berkeley Big O (video)
Amortized Analysis (video)
TopCoder (includes recurrence relations and master theorem):
- Computational Complexity: Section 1
- Computational Complexity: Section 2
Cheat sheet
[Review] Big-O notation in 5 minutes (video)

Well, that's about enough of that.

When you go through "Cracking the Coding Interview", there is a chapter on this, and at the end there is a quiz to see if you can identify the runtime complexity of different algorithms. It's a super review and test.

Data Structures

Arrays
- About Arrays:
  - Arrays CS50 Harvard University
  - Arrays (video)
  - UC Berkeley CS61B - Linear and Multi-Dim Arrays (video) (Start watching from 15m 32s)
  - Dynamic Arrays (video)
  - Jagged Arrays (video)
- Implement a vector (mutable array with automatic resizing):
  - Practice coding using arrays and pointers, and pointer math to jump to an index instead of using indexing.
  - New raw data array with allocated memory
    - can allocate int array under the hood, just not use its features
    - start with 16, or if starting number is greater, use power of 2 - 16, 32, 64, 128
  - size() - number of items
  - capacity() - number of items it can hold
  - is_empty()
  - at(index) - returns item at given index, blows up if index out of bounds
  - push(item)
  - insert(index, item) - inserts item at index, shifts that index's value and trailing elements to the right
  - prepend(item) - can use insert above at index 0
  - pop() - remove from end, return value
  - delete(index) - delete item at index, shifting all trailing elements left
  - remove(item) - looks for value and removes index holding it (even if in multiple places)
  - find(item) - looks for value and returns first index with that value, -1 if not found
  - resize(new_capacity) // private function
    - when you reach capacity, resize to double the size
    - when popping an item, if size is 1/4 of capacity, resize to half
- Time
  - O(1) to add/remove at end (amortized for allocations for more space), index, or update
  - O(n) to insert/remove elsewhere
- Space
  - contiguous in memory, so proximity helps performance
  - space needed = (array capacity, which is >= n) * size of item, but even if 2n, still O(n)
Linked Lists
- Description:
  - Linked Lists CS50 Harvard University - this builds the intuition.
  - Singly Linked Lists (video)
  - CS 61B - Linked Lists 1 (video)
  - CS 61B - Linked Lists 2 (video)
  - [Review] Linked lists in 4 minutes (video)
- C Code (video) - not the whole video, just portions about Node struct and memory allocation
- Linked List vs Arrays:
  - Core Linked Lists Vs Arrays (video)
  - In The Real World Linked Lists Vs Arrays (video)
- Why you should avoid linked lists (video)
- Gotcha: you need pointer to pointer knowledge: (for when you pass a pointer to a function that may change the address where that pointer points) This page is just to get a grasp on ptr to ptr. I don't recommend this list traversal style. Readability and maintainability suffer due to cleverness.
  - Pointers to Pointers
- Implement (I did with tail pointer & without):
  - size() - returns number of data elements in list
  - empty() - bool returns true if empty
  - value_at(index) - returns the value of the nth item (starting at 0 for first)
  - push_front(value) - adds an item to the front of the list
  - pop_front() - remove front item and return its value
  - push_back(value) - adds an item at the end
  - pop_back() - removes end item and returns its value
  - front() - get value of front item
  - back() - get value of end item
  - insert(index, value) - insert value at index, so current item at that index is pointed to by new item at index
  - erase(index) - removes node at given index
  - value_n_from_end(n) - returns the value of the node at nth position from the end of the list
  - reverse() - reverses the list
  - remove_value(value) - removes the first item in the list with this value
- Doubly-linked List
  - Description (video)
  - No need to implement
Stack
- Stacks (video)
- [Review] Stacks in 3 minutes (video)
- Will not implement. Implementing with array is trivial
Queue
- Queue (video)
- Circular buffer/FIFO
- [Review] Queues in 3 minutes (video)
- Implement using linked-list, with tail pointer:
  - enqueue(value) - adds value at position at tail
  - dequeue() - returns value and removes least recently added element (front)
  - empty()
- Implement using fixed-sized array:
  - enqueue(value) - adds item at end of available storage
  - dequeue() - returns value and removes least recently added element
  - empty()
  - full()
- Cost:
  - a bad implementation using linked list where you enqueue at head and dequeue at tail would be O(n) because you'd need the next to last element, causing a full traversal each dequeue
  - enqueue: O(1) (amortized, linked list and array [probing])
  - dequeue: O(1) (linked list and array)
  - empty: O(1) (linked list and array)
Hash table
- Videos:
- Online Courses:
  - Core Hash Tables (video)
  - Data Structures (video)
  - Phone Book Problem (video)
  - distributed hash tables:
    - Instant Uploads And Storage Optimization In Dropbox (video)
    - Distributed Hash Tables (video)
- Implement with array using linear probing
  - hash(k, m) - m is size of hash table
  - add(key, value) - if key already exists, update value
  - exists(key)
  - get(key)
  - remove(key)

More Knowledge

Binary search
- Binary Search (video)
- Binary Search (video)
- detail
- blueprint
- [Review] Binary search in 4 minutes (video)
- Implement:
  - binary search (on sorted array of integers)
  - binary search using recursion
Bitwise operations
- Bits cheat sheet - you should know many of the powers of 2 from (2^1 to 2^16 and 2^32)
- Get a really good understanding of manipulating bits with: &, |, ^, ~, >>, <<
- 2s and 1s complement
- Count set bits
- Swap values:
  - Swap
- Absolute value:
  - Absolute Integer

Trees

Trees - Intro
- Intro to Trees (video)
- Tree Traversal (video)
- BFS(breadth-first search) and DFS(depth-first search) (video)
  - BFS notes:
    - level order (BFS, using queue)
    - time complexity: O(n)
    - space complexity: best: O(1), worst: O(n/2)=O(n)
  - DFS notes:
    - time complexity: O(n)
    - space complexity: best: O(log n) - avg. height of tree worst: O(n)
    - inorder (DFS: left, self, right)
    - postorder (DFS: left, right, self)
    - preorder (DFS: self, left, right)
- [Review] Breadth-first search in 4 minutes (video)
- [Review] Depth-first search in 4 minutes (video)
- [Review] Tree Traversal (playlist) in 11 minutes (video)
Binary search trees: BSTs
- Binary Search Tree Review (video)
- Introduction (video)
- MIT (video)
- C/C++:
- Implement:
  - insert // insert value into tree
  - get_node_count // get count of values stored
  - print_values // prints the values in the tree, from min to max
  - delete_tree
  - is_in_tree // returns true if given value exists in the tree
  - get_height // returns the height in nodes (single node's height is 1)
  - get_min // returns the minimum value stored in the tree
  - get_max // returns the maximum value stored in the tree
  - is_binary_search_tree
  - delete_value
  - get_successor // returns next-highest value in tree after given value, -1 if none
Heap / Priority Queue / Binary Heap
- visualized as a tree, but is usually linear in storage (array, linked list)
- Heap
- Introduction (video)
- Binary Trees (video)
- Tree Height Remark (video)
- Basic Operations (video)
- Complete Binary Trees (video)
- Pseudocode (video)
- Heap Sort - jumps to start (video)
- Heap Sort (video)
- Building a heap (video)
- MIT: Heaps and Heap Sort (video)
- CS 61B Lecture 24: Priority Queues (video)
- Linear Time BuildHeap (max-heap)
- [Review] Heap (playlist) in 13 minutes (video)
- Implement a max-heap:
  - insert
  - sift_up - needed for insert
  - get_max - returns the max item, without removing it
  - get_size() - return number of elements stored
  - is_empty() - returns true if heap contains no elements
  - extract_max - returns the max item, removing it
  - sift_down - needed for extract_max
  - remove(x) - removes item at index x
  - heapify - create a heap from an array of elements, needed for heap_sort
  - heap_sort() - take an unsorted array and turn it into a sorted array in-place using a max heap or min heap

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

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

Recursion
- Stanford lectures on recursion & backtracking:
- When it is appropriate to use it?
- How is tail recursion better than not?
  - What Is Tail Recursion Why Is It So Bad?
  - Tail Recursion (video)
- 5 Simple Steps for Solving Any Recursive Problem(video)
Backtracking Blueprint: Java Python
Dynamic Programming
- You probably won't see any dynamic programming problems in your interview, but it's worth being able to recognize a problem as being a candidate for dynamic programming.
- This subject can be pretty difficult, as each DP soluble problem must be defined as a recursion relation, and coming up with it can be tricky.
- I suggest looking at many examples of DP problems until you have a solid understanding of the pattern involved.
- Videos:
- Yale Lecture notes:
  - Dynamic Programming
- Coursera:
Design patterns
- Quick UML review (video)
- Learn these patterns:
  - strategy
  - singleton
  - adapter
  - prototype
  - decorator
  - visitor
  - factory, abstract factory
  - facade
  - observer
  - proxy
  - delegate
  - command
  - state
  - memento
  - iterator
  - composite
  - flyweight
- Series of videos (27 videos)
- Book: Head First Design Patterns
  - I know the canonical book is "Design Patterns: Elements of Reusable Object-Oriented Software", but Head First is great for beginners to OO.
- Handy reference: 101 Design Patterns & Tips for Developers
Combinatorics (n choose k) & Probability
- Math Skills: How to find Factorial, Permutation and Combination (Choose) (video)
- Make School: Probability (video)
- Make School: More Probability and Markov Chains (video)
- Khan Academy:
  - Course layout:
    - Basic Theoretical Probability
  - Just the videos - 41 (each are simple and each are short):
    - Probability Explained (video)
NP, NP-Complete and Approximation Algorithms
- Know about the most famous classes of NP-complete problems, such as traveling salesman and the knapsack problem, and be able to recognize them when an interviewer asks you them in disguise.
- Know what NP-complete means.
- Computational Complexity (video)
- Simonson:
- Skiena:
- Complexity: P, NP, NP-completeness, Reductions (video)
- Complexity: Approximation Algorithms (video)
- Complexity: Fixed-Parameter Algorithms (video)
- Peter Norvig discusses near-optimal solutions to traveling salesman problem:
  - Jupyter Notebook
- Pages 1048 - 1140 in CLRS if you have it.
How computers process a program
Caches
- LRU cache:
- CPU cache:
  - MIT 6.004 L15: The Memory Hierarchy (video)
  - MIT 6.004 L16: Cache Issues (video)
Processes and Threads
- Computer Science 162 - Operating Systems (25 videos):
  - for processes and threads see videos 1-11
  - Operating Systems and System Programming (video)
- What Is The Difference Between A Process And A Thread?
- Covers:
  - Processes, Threads, Concurrency issues
    - Difference between processes and threads
    - Processes
    - Threads
    - Locks
    - Mutexes
    - Semaphores
    - Monitors
    - How they work?
    - Deadlock
    - Livelock
  - CPU activity, interrupts, context switching
  - Modern concurrency constructs with multicore processors
  - Paging, segmentation and virtual memory (video)
  - Interrupts (video)
  - Process resource needs (memory: code, static storage, stack, heap, and also file descriptors, i/o)
  - Thread resource needs (shares above (minus stack) with other threads in the same process but each has its own pc, stack counter, registers, and stack)
  - Forking is really copy on write (read-only) until the new process writes to memory, then it does a full copy.
  - Context switching
    - How context switching is initiated by the operating system and underlying hardware?
- threads in C++ (series - 10 videos)
- CS 377 Spring '14: Operating Systems from University of Massachusetts
- concurrency in Python (videos):
Testing
- To cover:
  - how unit testing works
  - what are mock objects
  - what is integration testing
  - what is dependency injection
- Agile Software Testing with James Bach (video)
- Open Lecture by James Bach on Software Testing (video)
- Steve Freeman - Test-Driven Development (that’s not what we meant) (video)
  - slides
- Dependency injection:
  - video
  - Tao Of Testing
- How to write tests
String searching & manipulations
If you need more detail on this subject, see "String Matching" section in Additional Detail on Some Subjects.
Tries
- Note there are different kinds of tries. Some have prefixes, some don't, and some use string instead of bits to track the path
- I read through code, but will not implement
- Sedgewick - Tries (3 videos)
- Notes on Data Structures and Programming Techniques
- Short course videos:
- The Trie: A Neglected Data Structure
- TopCoder - Using Tries
- Stanford Lecture (real world use case) (video)
- MIT, Advanced Data Structures, Strings (can get pretty obscure about halfway through) (video)
Floating Point Numbers
- simple 8-bit: Representation of Floating Point Numbers - 1 (video - there is an error in calculations - see video description)
Unicode
- The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets
- What Every Programmer Absolutely, Positively Needs To Know About Encodings And Character Sets To Work With Text
Endianness
- Big And Little Endian
- Big Endian Vs Little Endian (video)
- Big And Little Endian Inside/Out (video)
  - Very technical talk for kernel devs. Don't worry if most is over your head.
  - The first half is enough.
Networking
- If you have networking experience or want to be a reliability engineer or operations engineer, expect questions
- Otherwise, this is just good to know
- Khan Academy
- UDP and TCP: Comparison of Transport Protocols (video)
- TCP/IP and the OSI Model Explained! (video)
- Packet Transmission across the Internet. Networking & TCP/IP tutorial. (video)
- HTTP (video)
- SSL and HTTPS (video)
- SSL/TLS (video)
- HTTP 2.0 (video)
- Video Series (21 videos) (video)
- Subnetting Demystified - Part 5 CIDR Notation (video)
- Sockets:
  - Java - Sockets - Introduction (video)
  - Socket Programming (video)

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.

Series of 2-3 minutes short subject videos (23 videos)
- Videos
Series of 2-5 minutes short subject videos - Michael Sambol (46 videos):
- Videos
- Code Examples
Sedgewick Videos - Algorithms I
Sedgewick Videos - Algorithms II

Update Your Resume

See Resume prep information in the books: "Cracking The Coding Interview" and "Programming Interviews Exposed"
"This Is What A GOOD Resume Should Look Like" by Gayle McDowell (author of Cracking the Coding Interview),
- Note by the author: "This is for a US-focused resume. CVs for India and other countries have different expectations, although many of the points will be the same."
"Step-by-step resume guide" by Tech Interview Handbook
- Detailed guide on how to set up your resume from scratch, write effective resume content, optimize it, and test your resume

Interview Process & General Interview Prep

Mock Interviews:

Gainlo.co: Mock interviewers from big companies - I used this and it helped me relax for the phone screen and on-site interview
Pramp: Mock interviews from/with peers - peer-to-peer model of practice interviews
interviewing.io: Practice mock interview with senior engineers - anonymous algorithmic/systems design interviews with senior engineers from FAANG anonymously
Meetapro: Mock interviews with top FAANG interviewers - an Airbnb-style mock interview/coaching platform.

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 at least one answer 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 the answers, 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 the work/life balance?

Once You've Got The Job

Congratulations!

Keep learning.

You're never really done.

*****************************************************************************************************
*****************************************************************************************************

Everything below this point is optional. It is NOT needed for an entry-level interview.
However, 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.

*****************************************************************************************************
*****************************************************************************************************

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-Oriented Software
- AKA the "Gang Of Four" book, or GOF
- The canonical design patterns book
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.
    - This book is better as an algorithm reference, and not something you read cover to cover.
- Can rent it on Kindle
- Answers:
  - Solutions
- Errata
Algorithm (Jeff Erickson)
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

System Design, Scalability, Data Handling

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

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.

Compilers
- How a Compiler Works in ~1 minute (video)
- Harvard CS50 - Compilers (video)
- C++ (video)
- Understanding Compiler Optimization (C++) (video)
Emacs and vi(m)
- Familiarize yourself with a unix-based code editor
- vi(m):
- emacs:
- The Absolute Beginner's Guide to Emacs (video by David Wilson)
- The Absolute Beginner's Guide to Emacs (notes by David Wilson)
Unix command line tools
- I filled in the list below from good tools.
- bash
- cat
- grep
- sed
- awk
- curl or wget
- sort
- tr
- uniq
- strace
- tcpdump
Information theory (videos)
- Khan Academy
- More about Markov processes:
- See more in MIT 6.050J Information and Entropy series below
Parity & Hamming Code (videos)
- Intro
- Parity
- Hamming Code:
  - Error detection
  - Error correction
- Error Checking
Entropy
- Also see videos below
- Make sure to watch information theory videos first
- Information Theory, Claude Shannon, Entropy, Redundancy, Data Compression & Bits (video)
Cryptography
- Also see videos below
- Make sure to watch information theory videos first
- Khan Academy Series
- Cryptography: Hash Functions
- Cryptography: Encryption
Compression
- Make sure to watch information theory videos first
- Computerphile (videos):
- Compressor Head videos
- (optional) Google Developers Live: GZIP is not enough!
Computer Security
- MIT (23 videos)
Garbage collection
- GC in Python (video)
- Deep Dive Java: Garbage Collection is Good!
- Deep Dive Python: Garbage Collection in CPython (video)
Parallel Programming
- Coursera (Scala)
- Efficient Python for High Performance Parallel Computing (video)
Messaging, Serialization, and Queueing Systems
- Thrift
  - Tutorial
- Protocol Buffers
  - Tutorials
- gRPC
  - gRPC 101 for Java Developers (video)
- Redis
  - Tutorial
- Amazon SQS (queue)
- Amazon SNS (pub-sub)
- RabbitMQ
  - Get Started
- Celery
  - First Steps With Celery
- ZeroMQ
  - Intro - Read The Manual
- ActiveMQ
- Kafka
- MessagePack
- Avro
A*
- A Search Algorithm
- A* Pathfinding (E01: algorithm explanation) (video)
Fast Fourier Transform
- An Interactive Guide To The Fourier Transform
- What is a Fourier transform? What is it used for?
- What is the Fourier Transform? (video)
- Divide & Conquer: FFT (video)
- Understanding The FFT
Bloom Filter
- Given a Bloom filter with m bits and k hashing functions, both insertion and membership testing are O(k)
- Bloom Filters (video)
- Bloom Filters | Mining of Massive Datasets | Stanford University (video)
- Tutorial
- How To Write A Bloom Filter App
HyperLogLog
- How To Count A Billion Distinct Objects Using Only 1.5KB Of Memory
Locality-Sensitive Hashing
- Used to determine the similarity of documents
- The opposite of MD5 or SHA which are used to determine if 2 documents/strings are exactly the same
- Simhashing (hopefully) made simple
van Emde Boas Trees
- Divide & Conquer: van Emde Boas Trees (video)
- MIT Lecture Notes
Augmented Data Structures
- CS 61B Lecture 39: Augmenting Data Structures
Balanced search trees
- Know at least one type of balanced binary tree (and know how it's implemented):
- "Among balanced search trees, AVL and 2/3 trees are now passé, and red-black trees seem to be more popular. A particularly interesting self-organizing data structure is the splay tree, which uses rotations to move any accessed key to the root." - Skiena
- Of these, I chose to implement a splay tree. From what I've read, you won't implement a balanced search tree in your interview. But I wanted exposure to coding one up and let's face it, splay trees are the bee's knees. I did read a lot of red-black tree code
  - Splay tree: insert, search, delete functions If you end up implementing red/black tree try just these:
  - Search and insertion functions, skipping delete
- I want to learn more about B-Tree since it's used so widely with very large data sets
- Self-balancing binary search tree
- AVL trees
  - In practice: From what I can tell, these aren't used much in practice, but I could see where they would be: The AVL tree is another structure supporting O(log n) search, insertion, and removal. It is more rigidly balanced than red–black trees, leading to slower insertion and removal but faster retrieval. This makes it attractive for data structures that may be built once and loaded without reconstruction, such as language dictionaries (or program dictionaries, such as the opcodes of an assembler or interpreter)
  - MIT AVL Trees / AVL Sort (video)
  - AVL Trees (video)
  - AVL Tree Implementation (video)
  - Split And Merge
  - [Review] AVL Trees (playlist) in 19 minutes (video)
- Splay trees
  - In practice: Splay trees are typically used in the implementation of caches, memory allocators, routers, garbage collectors, data compression, ropes (replacement of string used for long text strings), in Windows NT (in the virtual memory, networking and file system code) etc
  - CS 61B: Splay Trees (video)
  - MIT Lecture: Splay Trees:
    - Gets very mathy, but watch the last 10 minutes for sure.
    - Video
- Red/black trees
  - These are a translation of a 2-3 tree (see below).
  - In practice: Red–black trees offer worst-case guarantees for insertion time, deletion time, and search time. Not only does this make them valuable in time-sensitive applications such as real-time applications, but it makes them valuable building blocks in other data structures which provide worst-case guarantees; for example, many data structures used in computational geometry can be based on red–black trees, and the Completely Fair Scheduler used in current Linux kernels uses red–black trees. In the version 8 of Java, the Collection HashMap has been modified such that instead of using a LinkedList to store identical elements with poor hashcodes, a Red-Black tree is used
  - Aduni - Algorithms - Lecture 4 (link jumps to starting point) (video)
  - Aduni - Algorithms - Lecture 5 (video)
  - Red-Black Tree
  - An Introduction To Binary Search And Red Black Tree
  - [Review] Red-Black Trees (playlist) in 30 minutes (video)
- 2-3 search trees
  - In practice: 2-3 trees have faster inserts at the expense of slower searches (since height is more compared to AVL trees).
  - You would use 2-3 tree very rarely because its implementation involves different types of nodes. Instead, people use Red Black trees.
  - 23-Tree Intuition and Definition (video)
  - Binary View of 23-Tree
  - 2-3 Trees (student recitation) (video)
- 2-3-4 Trees (aka 2-4 trees)
  - In practice: For every 2-4 tree, there are corresponding red–black trees with data elements in the same order. The insertion and deletion operations on 2-4 trees are also equivalent to color-flipping and rotations in red–black trees. This makes 2-4 trees an important tool for understanding the logic behind red–black trees, and this is why many introductory algorithm texts introduce 2-4 trees just before red–black trees, even though 2-4 trees are not often used in practice.
  - CS 61B Lecture 26: Balanced Search Trees (video)
  - Bottom Up 234-Trees (video)
  - Top Down 234-Trees (video)
- N-ary (K-ary, M-ary) trees
  - note: the N or K is the branching factor (max branches)
  - binary trees are a 2-ary tree, with branching factor = 2
  - 2-3 trees are 3-ary
  - K-Ary Tree
- B-Trees
  - Fun fact: it's a mystery, but the B could stand for Boeing, Balanced, or Bayer (co-inventor).
  - In Practice: B-Trees are widely used in databases. Most modern filesystems use B-trees (or Variants). In addition to its use in databases, the B-tree is also used in filesystems to allow quick random access to an arbitrary block in a particular file. The basic problem is turning the file block i address into a disk block (or perhaps to a cylinder-head-sector) address
  - B-Tree
  - B-Tree Datastructure
  - Introduction to B-Trees (video)
  - B-Tree Definition and Insertion (video)
  - B-Tree Deletion (video)
  - MIT 6.851 - Memory Hierarchy Models (video) - covers cache-oblivious B-Trees, very interesting data structures - the first 37 minutes are very technical, may be skipped (B is block size, cache line size)
  - [Review] B-Trees (playlist) in 26 minutes (video)
k-D Trees
- Great for finding number of points in a rectangle or higher dimension object
- A good fit for k-nearest neighbors
- kNN K-d tree algorithm (video)
Skip lists
- "These are somewhat of a cult data structure" - Skiena
- Randomization: Skip Lists (video)
- For animations and a little more detail
Network Flows
- Ford-Fulkerson in 5 minutes — Step by step example (video)
- Ford-Fulkerson Algorithm (video)
- Network Flows (video)
Disjoint Sets & Union Find
- UCB 61B - Disjoint Sets; Sorting & selection (video)
- Sedgewick Algorithms - Union-Find (6 videos)
Math for Fast Processing
- Integer Arithmetic, Karatsuba Multiplication (video)
- The Chinese Remainder Theorem (used in cryptography) (video)
Treap
- Combination of a binary search tree and a heap
- Treap
- Data Structures: Treaps explained (video)
- Applications in set operations
Linear Programming (videos)
- Linear Programming
- Finding minimum cost
- Finding maximum value
- Solve Linear Equations with Python - Simplex Algorithm
Geometry, Convex hull (videos)
- Graph Alg. IV: Intro to geometric algorithms - Lecture 9
- Geometric Algorithms: Graham & Jarvis - Lecture 10
- Divide & Conquer: Convex Hull, Median Finding
Discrete math
- Computer Science 70, 001 - Spring 2015 - Discrete Mathematics and Probability Theory
- Discrete Mathematics by Shai Simonson (19 videos)
- Discrete Mathematics By IIT Ropar NPTEL

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?

SOLID
- Bob Martin SOLID Principles of Object Oriented and Agile Design (video)
- S - Single Responsibility Principle | Single responsibility to each Object
  - more flavor
- O - Open/Closed Principle | On production level Objects are ready for extension but not for modification
  - more flavor
- L - Liskov Substitution Principle | Base Class and Derived class follow ‘IS A’ Principle
  - more flavor
- I - Interface segregation principle | clients should not be forced to implement interfaces they don't use
  - Interface Segregation Principle in 5 minutes (video)
  - more flavor
- D -Dependency Inversion principle | Reduce the dependency In composition of objects.
  - Why Is The Dependency Inversion Principle And Why Is It Important
  - more flavor
Union-Find
More Dynamic Programming (videos)
Advanced Graph Processing (videos)
- Synchronous Distributed Algorithms: Symmetry-Breaking. Shortest-Paths Spanning Trees
- Asynchronous Distributed Algorithms: Shortest-Paths Spanning Trees
MIT Probability (mathy, and go slowly, which is good for mathy things) (videos):
Simonson: Approximation Algorithms (video)
String Matching
- Rabin-Karp (videos):
- Knuth-Morris-Pratt (KMP):
  - TThe Knuth-Morris-Pratt (KMP) String Matching Algorithm
- Boyer–Moore string search algorithm
  - Boyer-Moore String Search Algorithm
  - Advanced String Searching Boyer-Moore-Horspool Algorithms (video)
- Coursera: Algorithms on Strings
  - starts off great, but by the time it gets past KMP it gets more complicated than it needs to be
  - nice explanation of tries
  - can be skipped
Sorting
- Stanford lectures on sorting:
  - Lecture 15 | Programming Abstractions (video)
  - Lecture 16 | Programming Abstractions (video)
- Shai Simonson:
  - Algorithms - Sorting - Lecture 2 (video)
  - Algorithms - Sorting II - Lecture 3 (video)
- Steven Skiena lectures on sorting:
  - CSE373 2020 - Mergesort/Quicksort (video)
  - CSE373 2020 - Linear Sorting (video)
NAND To Tetris: Build a Modern Computer from First Principles

Video Series

Sit back and enjoy.

Computer Science Courses

Algorithms implementation

Multiple Algorithms implementation by Princeton University

Papers

Love classic papers?
1978: Communicating Sequential Processes
- implemented in Go
2003: The Google File System
- replaced by Colossus in 2012
2004: MapReduce: Simplified Data Processing on Large Clusters
- mostly replaced by Cloud Dataflow?
2006: Bigtable: A Distributed Storage System for Structured Data
2006: The Chubby Lock Service for Loosely-Coupled Distributed Systems
2007: Dynamo: Amazon’s Highly Available Key-value Store
- The Dynamo paper kicked off the NoSQL revolution
2007: What Every Programmer Should Know About Memory (very long, and the author encourages skipping of some sections)
2012: AddressSanitizer: A Fast Address Sanity Checker:
- paper
- video
2013: Spanner: Google’s Globally-Distributed Database:
- paper
- video
2015: Continuous Pipelines at Google
2015: High-Availability at Massive Scale: Building Google’s Data Infrastructure for Ads
2015: How Developers Search for Code: A Case Study
More papers: 1,000 papers

LICENSE

CC-BY-SA-4.0

jwasham/coding-interview-university

jwasham

Reviews

Repository Details

Coding Interview University

What is it?

Table of Contents

The Study Plan

Topics of Study

Getting the Job

Optional Extra Topics & Resources

Why use it?

How to use it

If you don't want to use git

If you're comfortable with git

Don't feel you aren't smart enough

A Note About Video Resources

Choose a Programming Language

For this Study Plan

For your Coding Interview

Books for Data Structures and Algorithms

C

Python

Java

C++

Interview Prep Books

If you have tons of extra time:

Don't Make My Mistakes

1. You Won't Remember it All

2. Use Flashcards

3. Do Coding Interview Questions While You're Learning

4. Focus

What you won't see covered

The Daily Plan

Coding Question Practice

Coding Problems

Let's Get Started

Algorithmic complexity / Big-O / Asymptotic analysis

Data Structures

Arrays

Linked Lists

Stack

Queue

Hash table

More Knowledge

Binary search

Bitwise operations

Trees

Trees - Intro

Binary search trees: BSTs

Heap / Priority Queue / Binary Heap

Sorting

Graphs

Even More Knowledge

Recursion

Dynamic Programming

Design patterns

Combinatorics (n choose k) & Probability

NP, NP-Complete and Approximation Algorithms

How computers process a program

Caches

Processes and Threads

Testing

String searching & manipulations

Tries

Floating Point Numbers

Unicode

Endianness

Networking