Cracking the Facebook Coding Interview

Gayle L.McDowell | Founder / CEO

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Cracking the FacebookCoding InterviewI <3 Facebook!

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Hi! I’m Gayle Laakmann McDowell

Author Interview Coach Interview Consulting

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Behavioral Questions

The soft squishy stuff.

The Pitch / Resume Walk-Through

Your Past Work

1 – 2 Hard Projects Hard / cool You were central Technical depth

All Past Work Challenges,

architecture, tradeoffs, mistakes, successes, motivations

What did YOU do?

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Gayle Laakmann McDowell

Be PASSIONATE

Be KNOWLEDGEABLE

Be a GOOD TEAMMATE

Technical QuestionsWhy why why why why why meeeee02

ReallyHappens

Knowledge Questions + Coding

Design/Scalability + Coding

Algorithms/Problem Solving + Coding

Knowledge Questions

How do indices work in SQL?

Knowledge Questions

If you list it, know it

If you don’t know it, admit it Derive it if

possible.

Design

How would you design TinyURL?

ToApproach

WWYDAW

hatouldouotork

ToApproach

copeey componentsdentify issuesepair

ToApproach

① Scope the Problem Ask questions Make appropriate

assumptions

② Define Key Components

Can be somewhat naïve

③ Identify Issues Bottlenecks, tradeoffs

④ Repair & Redesign

How to Act

DRIVE Lead the

process Be open about

issues

TEAMWORK Be open to

feedback Tweak as

necessary

Prepare

Read about design of major companies Twitter, Facebook,

Quora, Google, etc. Think about WHY

they’re designed that way

Learn/review key concepts Task queues,

databases, sharding, etc.

Practice questions

Algorithm Preparation

Problem solving, not puzzles!

Strong CS fundamentals

Analytical skills

Make tradeoffs

Push through hard problems

Communication

How you think

Essential Knowledge

Data Structures

Algorithms Concepts

ArrayLists Merge Sort Big O Time

Hash Tables Quick Sort Big O Space

Trees (+ Tries) Breadth-First Search

Recursion

Graphs Depth-First Search

Memoization / Dynamic Programming

Stacks / Queues Binary Search

Preparation

Implement DS/Algorithms MASTER Big O Practice with interview questions Code on paper/whiteboard Mock interviews

PUSH YOURSELF!

Solving Algorithms

How to… attempt to solve a hard problem

is NOTexpected

To know the answers To solve immediately To code perfectly

(It’s nice. It just doesn’t

happen*.)

* Okay fine. It happened once, in 2000+ hiring packets.

ISexpected

Be excited about hard problems

More than just “correct”

Drive! Keep trying when

stuck Write real code

Show me how you think!

ToApproach

“Reso

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1Listen (for clues)

What’s the clue?

Anagram server Ex: rates -> aster, stare, taser,

Clue: why is it on a server?

2Draw an Example

Big Enough

General Purpose

Ex: Intersection of Two Sorted Arrays

Most people draw something like this:

[1, 12, 15, 19][2, 12, 13, 20]

Too small Too special-case-y • same size, one common element, same

Ex: Intersection of Two Sorted Arrays

Better:

[1, 12, 15, 19, 20, 21][2, 15, 17, 19, 21, 25,

Big No special cases

3Brute Force / Naive

Stupid & terrible is okay!

4Optimize

Walk through

brute force

Look for optimizations

Techniques to Develop Algorithms

OptimizeA. BUDB. Space/timeC. Do it yourself

SolveD. RecursionE. Solve

“incorrectly”F. Other data

structures

Push yourself!

(A) Look for BUD

BottlenecksUnnecessary workDuplicated work

What’s the bottleneck?

Ex: counting the intersection[1, 12, 15, 19, 20, 21][2, 15, 17, 19, 21, 25, 27]

Bottleneck: searching

What’s unnecessary?