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Coding Interview University אוניברסיטיה של ראיונות קוד

על מה מדובר כאן?

בהתחלה, זאת היתה רשימה קצרה של נושאי לימוד כדי להיות מהנדס תוכנה, אבל עם הזמן הפרוייקט צמח להיות מה שאפשר לראות כיום. לאחר סיום תוכנית הלימודים הזאת, התקבלתי לעבוד כמפתח תוכנה באמזון! את\אתה כנראה לא תצטרכו ללמוד באותה כמות שאני למדתי. בכל אופן כל מה שאתם זקוקים לו נמצא פה.

למדתי בין 8-12 שעות ביום, למשך מספר חודשים. זהו הסיפור שלי: למה למדתי במשרה מלאה למשך שמונה חודשים בשביל ראיון עבודה בגוגל.

אנא שימו לב: את\ה לא צריכים ללמוד באותה הכמות שאני למדתי. בזבזתי זמן רב על דברים שלא הייתי צריך לדעת. מידע נוסף על כך בהמשך. אני .אעזור לך לסיים מבלי לבזבז את זמנכם היקר

הפריטים ברשימה המובאת כאן יכינו אותך לראיון טכני פחות או יותר בכל חברת טכנולוגיה, כולל הענקיות: אמזון, פייסבוק, גוגל ומייקרוסופט.


שיהיה המון בהצלחה!

חלק גדול מהתכנים לקוחים מהאתר המצויין של סטיב יגיי: המשרה הזו בגוגל? שלך! "Get that job at Google"

ערכתי וקיצרתי עבורכם את מה שלדעתי נדרש עבור מהנדס תוכנה מתחיל עם מעט ניסיון מתוך המקורות הנ"ל. עבור אלו מכם הרוצים הסבת מקצוע מפיתוח אתרים או פיתוח תוכנה בתפקידים כאלו ואחרים שאינם הנדסת תוכנה. עבור אלו מכם בעלי הניסיון כמהנדסי תוכנה, בייחוד אם ישנן שנות ניסיון רבות כמהנדס תוכנה בתחום, המשימות הנ"ל עלולות להיות קלות מדי והציפיות מהם בראיון לגוגל יהיו הרבה יותר גבוהות. במידה ואתם בעלי מספר שנות ניסיון כמפתחים, גוגל רואה בהנדסת תוכנה משהו שונה מתכנות נטו ולכן הדרישות הן שונות וגבוהות יותר. עבור מהנדסי המערכת ומהנדסי האמינות שביניכם, השקיעו יותר בחומר המופיע ב"רשימת הרשות" זוהי רשימת משימות המכילה נושאי רשות עבור מהנדס תוכנה.

תוכן העניינים Table of Contents

---------------- מתחת לקו זה נמצא חומר הרשות שמומלץ לרקע כללי או למהנדסי מערכת ותפקידים נוספים ----------------

למה להשתמש בזה?

אני מתכונן לראיון בגוגל תוך כדי יישום תוכנית זו. בניתי את הרשת, בניתי שרותים ברשת, אני בונה ומשיק סטארטאפים מאז 1997. יש לי תואר בכלכלה, לא במדעי המחשב. הייתה לי קריירה מוצלחת אבל אני חולם לעבוד בגוגל. אני רוצה להתקדם ולעבוד עם מערכות גדולות יותר ולקבל הבנה מעמיקה של מערכות מחשוב, אלגוריתמים יעילים, התנהגות בסיסי נתונים, I'm following this plan to prepare for my Google interview. I've been building the web, building services, and launching startups since 1997. I have an economics degree, not a CS degree. I've been very successful in my career, but I want to work at Google. I want to progress into larger systems and get a real understanding of computer systems, algorithmic efficiency, data structure performance, low-level languages, and how it all works. And if you don't know any of it, Google won't hire you. When I started this project, I didn't know a stack from a heap, didn't know Big-O anything, anything about trees, or how to traverse a graph. If I had to code a sorting algorithm, I can tell ya it wouldn't have been very good. Every data structure I've ever used was built into the language, and I didn't know how they worked under the hood at all. I've 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've used a few multidimensional arrays in my life and thousands of associative arrays, but I've never created data structures from scratch.

But after going through this study plan I have high confidence I'll be hired. It's a long plan. It's going to take me months. If you are familiar with a lot of this already it will take you a lot less time.

איך להשתמש בזה

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 check progress.

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

    Fork a branch and follow the commands below

git checkout -b progress

git remote add jwasham https://github.com/jwasham/coding-interview-university

git fetch --all

Mark all boxes with X after you completed your changes

git add .

git commit -m "Marked x"

git rebase jwasham/main

git push --force

More about Github-flavored markdown

Get in a Googley Mood

Print out a "future Googler" sign (or two) and keep your eyes on the prize.

future Googler sign

האם קיבלתי את העבודה?

אני בתור כרגע. אני מקווה להתראיין בקרוב.

Thanks for the referral, JP.

Follow Along with Me

הסיפור שלי: Why I Studied Full-Time for 8 Months for a Google Interview

גם אני עובר את המסע. עקבו אחריי:

John Washam - Coding Interview University

אל תרדגישו שאתם לא חכמים מספיק

אודות גוגל

About Video Resources

Some videos are available only by enrolling in a Coursera, EdX, or Lynda.com 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. Lynda.com courses are not free.

I'd appreciate your help to add free and always-available public sources, such as YouTube videos to accompany the online course videos.
I like using university lectures.

תהליך הראיון והכנה כללית לראיון

Pick One Language for the Interview

I wrote this short article about it: Important: Pick One Language for the Google Interview

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

  • C++
  • Java
  • Python

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

  • JavaScript
  • Ruby

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

Read more about choices:

See language resources here

You'll see some C, C++, and Python learning included below, because I'm learning. There are a few books involved, see the bottom.

רשימת ספרים

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

Interview Prep

If you have tons of extra time:

מבנה המחשב

If short on time:

  • 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

If you have more time (I want this book):

Language Specific

You need to choose a language for the interview (see above). Here are my recommendations by language. I don't have resources for all languages. I welcome additions.

If you read though one of these, you should have all the data structures and algorithms knowledge you'll need to start doing coding problems. You can skip all the video lectures in this project, unless you'd like a review.

Additional language-specific resources here.

C++

I haven't read these two, but they are highly rated and written by Sedgewick. He's awesome.

If you have a better recommendation for C++, please let me know. Looking for a comprehensive resource.

Java

OR:

  • Data Structures and Algorithms in Java
    • by Goodrich, Tamassia, Goldwasser
    • used as optional text for CS intro course at UC Berkeley
    • see my book report on the Python version below. This book covers the same topics.

Python

Optional Books

Some people recommend these, but I think it's going overboard, unless you have many years of software engineering experience and expect a much harder interview:

  • 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.
    • To quote Yegge: "More than any other book it helped me understand just how astonishingly commonplace (and important) graph problems are – they should be part of every working programmer's toolkit. The book also covers basic data structures and sorting algorithms, which is a nice bonus. But the gold mine is the second half of the book, which is a sort of encyclopedia of 1-pagers on zillions of useful problems and various ways to solve them, without too much detail. Almost every 1-pager has a simple picture, making it easy to remember. This is a great way to learn how to identify hundreds of problem types."
    • Can rent it on kindle
    • Half.com is a great resource for textbooks at good prices.
    • Answers:
    • Errata

  • 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.
    • To quote Yegge: "But if you want to come into your interviews prepped, then consider deferring your application until you've made your way through that book."
    • Half.com is a great resource for textbooks at good prices.
    • aka CLR, sometimes CLRS, because Stein was late to the game

  • 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, much like Code Complete, but much shorter.

  • "Algorithms and Programming: Problems and Solutions" by Shen

    • A fine book, but after working through problems on several pages I got frustrated with the Pascal, do while loops, 1-indexed arrays, and unclear post-condition satisfaction results.
    • Would rather spend time on coding problems from another book or online coding problems.

לפני שאתם מתחילים

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

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.

Read please 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 and tablet, wherever I am.

Make your own for free:

  • Flashcards site repo
  • My flash cards database: 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 by Google.

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)

3. 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.

4. Focus

There are a lot of distractions that can take up valuable time. Focus and concentration are hard.

What you won't see covered

This big list all started as a personal to-do list made from Google interview coaching notes. These are prevalent technologies but were not mentioned in those notes:

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

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:

  • C - using structs and functions that take a struct * and something else as args.
  • C++ - without using built-in types
  • C++ - using built-in types, like STL's std::list for a linked list
  • 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
  • You may do Java or something else, this is just my thing.

You don't need all these. You need only one language for the interview.

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))
  • 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)

I may not have time to do all of these for every subject, but I'll try.

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

Algorithmic complexity / Big-O / Asymptotic analysis

מבנה נתונים

  • מערכים

    • Implement an automatically resizing vector.
    • Description:
    • 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:
    • C Code (video) - not the whole video, just portions about Node struct and memory allocation.
    • Linked List vs Arrays:
    • 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.
    • 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

  • מחסנית

  • תור

    • 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

ידע נוסף

עצים

מיונים

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.

You'll get more graph practice in Skiena's book (see Books section below) and the interview books

Even More Knowledge

System Design, Scalability, Data Handling

חזרה סופית

This section will have shorter videos that can you 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

My Process for Coding Interview (Book) Exercises

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.

my sofa whiteboard

Supplemental:

Read and Do Programming Problems (in this order):

See Book List above

תרגילי/אתגרי קידוד

ברגע שלמדתם מעל ומעבר, תתחילו להשתמש במה שלמדתם. תעשו אתגרי קידוד כל יום, כמה שאתם יכולים.

אתרים עם אתגרים:

ראיונות דמה:

Once you're closer to the interview

קורות חיים שלך

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 Google 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?

Once You've Got The Job

Congratulations!

Keep learning.

You're never really done.

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

Everything below this point is optional. These are my recommendations, not Google's.
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.

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

ספרים נוספים

לימודים נוספים

--

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

קורסים במדעי המחשב