Cracking the Coding Interview

1. Cracking the Coding Interview Advice and Strategies for Software Engineering and PM Interviews Gayle Laakmann McDowell Founder / CEO, CareerCup.com Author of The Google Resume and Cracking the Coding Interview McDowell | CareerCup.com | Palantir Oct 2012

2. My Background • Software Engineer @ Google, Microsoft & Apple • 3 Years on Google Hiring Committee • Interviewed 150+ candidates • Founder of CareerCup.com • Author • Cracking the Coding Interview • The Google Resume McDowell | CareerCup.com

3. Slides Posted Online posted at: www.technologywoman.com Click “Speaking Engagements” McDowell | CareerCup.com

4. McDowell | CareerCup.com

5. Interview Process McDowell | CareerCup.com

6. Big Company Evaluation (Devs) Testing aptitude, not knowledge McDowell | CareerCup.com

7. Start-Ups (Devs) • “Hit the ground running” • Do you know “their” technologies? • Entrepreneurial • Have you started things? • How much direction do you need? • Personality • Will you fit with the team? but… it varies! McDowell | CareerCup.com

8. PMs (Microsoft) & APMs (Google) • Communication Skills • User-Focused Thinking • Passion for Technology • Analytical Skills • Technical Skills (position dependent) McDowell | CareerCup.com

9. How You Are Judged How did you do RELATIVE to other candidates on the SAME question? It’s not about how quickly you solved the problem… … it’s about how quickly you solved it relative to other candidates. McDowell | CareerCup.com

10. Resumes & Application Process McDowell | CareerCup.com

11. How to Get an Interview • Build something! • Make a kick-ass resume Got a weekend free? It’s really not that hard. McDowell | CareerCup.com

12. How We Review Resumes • Pull resume out of giant stack • Spot-check: company names, positions, projects, schools. • Skim bullets for coding / impact “Glanced at,” not read. 15 – 30 seconds Reject Interview • Go to next resume & whine about how many more you have left. McDowell | CareerCup.com

13. How CS Resume Should Look Observe: No Objective! Objectives / summaries are almost always useless. One Page Only! Unless > 10 years exp. A Real Resume Format with organized columns Short (1 – 2 line bullets) Focus on Accomplishments not responsibilities GPAif at least 3.0 max (in-major, overall) 3 – 4 Projects Courses & independent Finished or unfinished List of Technical Skills Short! Cut the “fluff.”

14. Behavioral Questions McDowell | CareerCup.com

15. Goals of Your Answer • Answer the question. • Deliver a goodanswer. • Communicate well. • Nugget First • S.A.R.: Situation, Action, Result McDowell | CareerCup.com

16. Preparing for Behavioral Qs • Create Preparation Grid for Projects + Behavioral Grid [for PM & less tech. roles] McDowell | CareerCup.com

17. Technical SkillsInterview Prep McDowell | CareerCup.com

18. How to study • Study the basics • Complex algorithms generally unnecessary. • Practice solving questions • Don’t memorize! • See: CtCI & CareerCup.com • Push yourself! • Write code on paper McDowell | CareerCup.com

19. Data Structures • How to implement • When to use (pros / cons) McDowell | CareerCup.com

20. Algorithms • Implementation • Space vs. Time Complexity McDowell | CareerCup.com

21. Concepts • Not just a concept – know how to code! McDowell | CareerCup.com

22. Technical SkillsMastering the Interview McDowell | CareerCup.com

23. Types of “Serious” Questions • Product Design Questions • Estimation Questions • Software Engineering Questions • Coding & Algorithms • Object Oriented Design • Scalability McDowell | CareerCup.com

24. Product Design Questions How would you design an calculator for the blind? Design an elevator for a building. Pick a Google product. How would you improve it?

25. Product Design Questions: Why? • Communication & Structured Thinking • Ability to understand the user • Creativity • Business instincts / skills

26. Product Design Qs: Approach • Ask questions to resolve ambiguity • Understand the user • Structure the problem • Solve piece by piece

27. Estimation Questions How many tennis balls can fit in an SUV? How much money does Gmail make from ads every year? How much do New Yorkers spend on electricity each year?

28. Estimation Qs: Why? • Problem Solving • Basic Quantitative Skills

29. Estimation Qs: How to Approach • Ask questions to resolve ambiguity • Don’t make assumptions (yet) • Outline / Structure Your Approach • Break down the components • Assume numbers when necessary • State assumptions explicitly • Round numbers to make your math easier • Sanity Check • Do your numbers make sense?

30. Technical Questions • Ask Questions! • Questions are more ambiguous than they appear • Talk out loud • Show us how you think • Think critically • Does your algorithm really work? What’s the space and time complexity? • Code slowly and methodically • It’s not a race • Test your code • And make CAREFUL fixes. If you’ve heard a question before, admit it. McDowell | CareerCup.com

31. What does a “good coder” do? • Be methodical. Don’t try to rush. • Reasonably Bug Free • Thorough testing (and careful fixing) • Check for error conditions • Clean coding • Use other functions • Good use of data structures (define own if useful) • Concise and readable McDowell | CareerCup.com

32. Types of Interview Questions “Design a Parking Lot” “Reverse a Linked List” “Design a Web Crawler” McDowell | CareerCup.com

33. Types of Interview Questions McDowell | CareerCup.com

34. Algorithm Qs: Pattern Matching Q: Write code to reverse the order of words in a sentence. “dogs are cute” “cute are dogs” Similar to: reverse characters in a string. “dogs are cute” “etuc era sgod” A: Reverse full string, then reverse each word. McDowell | CareerCup.com

35. Algorithm Qs: Simplify & Generalize Q: Design algorithm to figure out if you can build a ransom note (array of strings) from a magazine (array of strings). Simplify: what if we used characters instead of strings?  Build array of character frequencies. Generalize: how we can extend answer to words? A: Build hashtable from word to frequency. McDowell | CareerCup.com

36. Algorithm Qs: Base Case & Build Q: Design algorithm to print subsets of set. {a, b, c}  {}, {a}, {b}, {c}, {a, b}, {a, c}, {b, c}, {a, b, c} S({}) {} S({a}) {}, {a} S({a, b}) {}, {a}, {b}, {a, b} S({a, b, c})  ? A: Build S(n) by cloning S(n-1) and adding n to the cloned sets. McDowell | CareerCup.com

37. Algorithm Qs: Data Structure Brainstorm Q: There are 10^10 possible phone #s. Explain how you could efficiently implement assignSpecificNum(num)and assignAnyAvailableNum(). Array (sorted)? Too slow to remove num. Linked list? Too slow to find specific num. Hash table? Can’t iterate through free nums. Tree? Ah-ha! A: Store free #s in BST. Remove when taken. McDowell | CareerCup.com

38. How To Solve Algorithm Questions Compare to similar problems. Solve first for a simplified / tweaked problem. Solve for n = 1, and build solution for n = 2. Try to apply data structure to solve problem. McDowell | CareerCup.com

39. Object Oriented Design Handle Ambiguity What about the question is ambiguous? Design the Core Objects What are the main objects in the system? Analyze Relationships How are the objects related to each other? Investigate Actions What are the main operations? McDowell | CareerCup.com

40. Object Oriented Design Handle Ambiguity Is it a single restaurant, or part of a chain? Design the Core Objects Guest, Party, Table, Server, Host, … Analyze Relationships Server and Host are both Employees… Investigate Actions A Party is seated at a Table by a Host… How would you design the data structures and objects for a restaurant? McDowell | CareerCup.com

41. System Design Handle Ambiguity What about the question is ambiguous? Make Believe Pretend there wasn’t so much data & solve Get Real Go back to the real problem. What breaks? Solve Problems Solve the issues you just found. McDowell | CareerCup.com

42. System Design Given millions of documents, find all documents which contain a list of words. Handle Ambiguity Do the words need to be in a specific order? Make Believe Assume everything can fit on one machine. Get Real Must split up data across machines. Solve Problems Divide hash table by file or by keyword? McDowell | CareerCup.com

43. Whew! All Done! <Gulp> This is a lot of stuff. Do I need to get everything right? McDowell | CareerCup.com

44. Evaluation is RELATIVE, not absolute. <Gulp> This is a lot of stuff. Do I need to get everything right? It’s not about how quickly you solved the problem… </Gulp> … it’s about how quickly you solved it relative to other candidates. McDowell | CareerCup.com

45. So RELAX! Interviews are supposed to be hard! Everyone makes mistakes. Everyone! McDowell | CareerCup.com

46. Final Thoughts McDowell | CareerCup.com

47. After Your Interview • Follow-up with your recruiter • No response != rejection • You have no idea how well/poorly you did. • Seriously. I know you think you do. But you don’t. • Lots of randomness. • So if you fail, get up and try again. McDowell | CareerCup.com

48. Other Resources • CareerCup.com • Interview Videos • iPhone App • Resume Review • Mock Interviews Sold Today Signed! {ask to add your name too} 5 stars! today today $15 $25 • Or, follow me online at… • twitter.com/gayle • facebook.com/gayle • technologywoman.com • gayle@careercup.com McDowell | CareerCup.com