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Facebook coding interview questions - Your complete coding interview guide

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Facebook coding interview questions - Your complete coding interview guide

Facebook is one of the top tech world companies. The company with excellent benefits, growth-based company culture, and top salaries which are at the level of only a few other companies. Many developers around the globe dream of working at Facebook.

Working at Facebook means being around smart people who are excited about what’s going on around them. This is a working place that both values and practices openness. The company has great tools and processes, cool technology/ problems/and products to work on, great/fun culture, lots of great free food/snacks/and drinks.

There is a mixture of prestige, good pay and benefits, significant potential rewards, and lots of hard work. The amount of hard work would be salaried. But the competition here is fierce. Facebook is on the lookout for the top candidates.

When choosing the candidates, that on which Facebook focuses is:

-> cultural fit,

->generalist knowledge,

-> ability to build within constraints,

-> expert coding skills.

In this article, I’ll provide coding questions for your better preparation, and will guide you step by step, to help you crack the Facebook coding interview.

We will cover:

  • interview process
  • coding questions and books for cracking the coding interview
  • How to prepare
    • Coding rounds
    • system design interview,
    • Behavioral round

So, let’s ace the coding interview.

1. Facebook coding interview

The interview process lasts 1.5 to 2 months (starting from resume submission). The interview process comprises 6 to 7 interviews, including 1 pre-screen interview, technical phone interview (with 1-2 coding questions), and 4-5 on-site interviews.

One Facebook Onsite interview has three sections:

  • The first section comprises 2 coding interviews using a whiteboard.
  • Second: 2 system design interviews.
  • Third on-site section: 1 cultural/behavioral interview.

1.1 There are two kinds of coding rounds at Facebook: practical and general.

1.1.1 Practical Coding Round:

In this round, you should know one programming language completely. At least how to read/write/open file, string manipulations, the internals of hashmap function, sorting of hashmap by key or values, beginning level of socket programming, HTTP calls, etc.

1.1.2 General Coding Round:

Expect to be more algorithmic or data structure-oriented this round. In this round, you can expect questions of medium to hard level.

1.2 Programming languages at Facebook

Facebook prefers Java, C++, Python, Ruby, and Perl.

1.3 In Facebook coding interview prepare for:

  • The Coding Problems.
  • The System Design Questions.
  • The Psychosocial Interview.
  • Expect success, but also be prepared for failure.

2. Facebook coding questions

Facebook interview questions focus on generalist knowledge on:

  • algorithms,
  • data structures,
  • time complexity.

2.1 Top 25 Facebook coding interview questions

Arrays and strings are essential skills to master for Facebook interviews. Facebook focuses mostly on them.

Interview help is your one-stop shop to prepare for the algorithms’ questions. Below, I’ll add 25 questions for your better coding interview preparation. If you complete it all, you’ll be very solid. Don’t skip the hard ones to only do the ‘easy’ and ‘mediums’. Do them all.

  1. Add strings

    https://leetcode.com/problems/add-strings/

  2. Add numbers

    https://leetcode.com/problems/add-two-numbers/

  3. Binary Tree Right Side View

    https://leetcode.com/problems/basic-calculator-ii/

  4. Basic Calculator II

    https://leetcode.com/problems/binary-tree-right-side-view/

  5. Count All Valid Pickup and Delivery Options

    https://leetcode.com/problems/count-all-valid-pickup-and-delivery-options/

2.2 20 more common Facebook coding interview questions

  1. Longest increasing subsequence from the array of integers (dynamic programming arrays)
  2. Unique paths in a grid (dynamic programming matrices)
  3. Design cache (system design)
  4. Design a highly consistent database (system design)
  5. Rotate a matrix (arrays)
  6. Find nth Fibonacci number (number theory)
  7. Find the square root of an integer using binary search (math search answer)
  8. Implement StrStr (string search)
  9. Minimum appends for Palindrome (strings)
  10. Find the largest rectangle in a histogram (stacks)
  11. Substring concatenation (incremental hash)
  12. Find largest distance between nodes in a tree (DFS)
  13. Find all unique triplets in an array, giving sum of zero (array)
  14. Find maximum path sum in the non-empty binary tree (binary tree)
  15. Find K closest points to origin for a list of points on a plane (search/sort)
  16. Write a function to compute intersection of arrays (sort/search)
  17. Design Facebook Messenger (system design)
  18. Group anagrams together in an array of strings (arrays/strings)
  19. Convert a BST to sorted circular doubly linked list (trees)
  20. Determine the order of letters in a dictionary (graphs/trees)

2.3 Books for cracking the coding interview

Facebook interviewers expect you to solve two coding questions in 45 minutes.

You should practice a lot of questions and practice how to solve two coding questions in that given time, so let’s do it together. We can help you level up your skills and calm your nerves. Join our platform and let’s practice.

Prepare For Your Interview Using Our Leet code Interview Preparation Program

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3. How to prepare for Facebook interview

Now you know what to expect in the interview, you also know what kind of questions to expect. So, often candidates ask how much time the preparation for the interview needs, and how to prepare. Below I’ll give you the concept, what to focus on while preparing for the Facebook interview.

Your focus should be on:

  • Practicing coding questions
  • Preparing for the system design interview
  • Preparing for behavioral round
  • Preparing the right questions for your interviewer

3.1 Preparing for coding rounds

There’s no ‘secret sauce’ to cracking the coding interview. It’s all about just getting in as much practice as you can, and solidifying your fundamentals. 3 months of practicing is enough to be successful. It’s important to use different tools while practicing coding. Facebook interviews focus on getting the code on to the whiteboard with almost no bugs the very first time. So, get a whiteboard and write away!

You can practice questions by yourself (Glassdoor for example, is an excellent source for that. I’d suggest answering the questions out-loud with a whiteboard or in a text editor, just as you would during an interview). Or, practice with a friend and perform mock interviews with each other. You can also use our platform and let us help you practice mock interviews.

3.2 Preparing for system design interview

At Facebook, you can expect system design questions, no matter what level you are interviewing for.

Don’t memorize answers on system design questions. Instead, learn the anatomy of a system design question. That way, you will crack the system design interviews.

For system design rounds, I recommend you a lot of practice. Take a look at the book: “Cracking design interviews”.

3.3 Behavioral round preparation

Through this round, interviewers look at whether you are a good fit for their culture. A high-level manager will ask you questions about your past job, motivation, etc. You should be prepared to talk about yourself. During this round, be open, focus on impact and build social value.

So, there’s nothing special you can do to prepare for this. I recommend you just to go through your past and collect instances where you took initiative, resolved conflicts, etc. The important thing is to practice how to convey that in the best possible way. Mock interviews are an excellent choice for practicing this.

3.4 Preparing the right questions for your interviewer

It’s an important part of the whole interview - the opportunity to determine if Facebook is a good fit for your lifestyle and needs. So, come prepared with the questions for your interviewers. The company appreciates this.

You should practice a lot of coding and system design interviews before the real thing.

I recommend you to use our peak-to- peak mock interviews platform for LeetCode preparation, system design preparation, and behavioral coaching. With proper preparation, the coding interviews will be much easier than you expect.

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Update: 2021-11-17