gayle mcdowell: cracking the coding interview
Post on 18-Oct-2014
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Talk video in youtube: http://www.youtube.com/watch?v=rEJzOhC5ZtQTRANSCRIPT
Cracking the Coding Interview
Advice and Strategies for Software Engineering Interviews
McDowell | NIT Trichy | Feb 2012 CareerCup.com
Gayle Laakmann McDowellFounder / CEO, CareerCup.com
Author of The Google Resume and Cracking the Coding Interview
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
My Background
• Software Engineer @ GOOG, MS & 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
Technical SkillsBehavioralApplying
Process
Slides Posted Online
posted at:www.technologywoman.com
Click “Speaking Engagements”
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Process
Evaluation
Structure
Applying
Experience
Resume
Soft Skills
Preparation
Interview
Tech Skills
Preparation
Interview
Interview Process
McDowell | CareerCup.com
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Big Company Evaluation (Coding)
IntelligenceCodingSkills
PersonalityExperience
Testing aptitude, not knowledge
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
How You Are Judged
How did you do RELATIVEto other candidates on
the SAME question?
… it’s about how quickly you solved it relative to
other candidates.
It’s not about how quickly you solved the problem…
Resumes & Application Process
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Indians are at a disadvantage
• Far away– Fewer recruiting opportunities
• Unfamiliar– Recruiters may not understand your
school, GPA, etc
• Language barrier / Cultural differences– Accents, grammar, accidental sexism
• Different / less experience– More emphasis in US on projects
Technical SkillsBehavioralApplying
Process
So what to do?
• Get equivalent experience • Translate GPA & other items• Use good grammar & punctuation– On resumes, cover letters, etc– No abbreviations, no sloppiness
• Be careful about your assumptions– Sexism is not acceptable in the U.S. Ever.
Technical SkillsBehavioralApplying
Process
Cheat Sheet for Indians (Grammar / Writing)
• Space after comma & period. Never before.– WRONG: “Hello .I am Gayle .”– RIGHT: “Hello. I am Gayle.”
• Questions need a question mark– WRONG: “Do you have one.”– RIGHT: “Do you have one?”
• No abbreviations– WRONG: “Ny1 dr?”– RIGHT: “Is anyone there?”
• Commands are rude (use a question)– WRONG: “Send it to me.”– RIGHT: “Would you mind sending it to me?”
Technical SkillsBehavioralApplying
Process
Cheat Sheet for Indians(Gender / Sexism)
• Mr. LastName / Ms. LastName– WRONG: Ms. Gayle– RIGHT: Ms. McDowell– But “Dear Gayle” is perfectly okay in U.S.
• “Guy” / “Guys” is not unisex* in the U.S.– WRONG: “I need to hire a really smart CS guy.”– *Except: “you guys” and “hey guys”
• Don’t assume that people are male / female– (Just don’t use Mr. / Ms. in emails!)
• It is EXTREMELY offensive to comment on someone’s looks– But a great way to get fired / rejected
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Cheat Sheet for Indians(Getting Experience)
• Build something!
• Make a kick-ass resume
Don’t waste your summers!
It’s really not that hard.
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
How We Review Resumes (U.S.)
1. Pull resume out of giant stack2. Spot-check: company names,
positions, projects, schools.3. Skim bullets to see if you’ve
written real code.
InterviewReject
4. Go to next resume & whine about how many more you have left.
“Glanced at,” not
read.15 – 30 seconds
How CS Resume Should Look (U.S.)
Short (1 – 2 line bullets)
3 – 4 ProjectsCourses & independentFinished or unfinished
List of Technical Skills
Short! Cut the “fluff.”
GPA - TranslatedWe don’t understand
“first class”
One Page Only!Unless > 10 years
exp.
A Real Resume Formatwith organized columns
Focus on Accomplishmentsnot responsibilities
Observe: No Objective!
Objectives / summaries are almost always
useless.
Behavioral Questions
McDowell | CareerCup.com
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Communication Tips
• Goals:– Answer the question.– Deliver a *good* answer.– Communicate well.
• Strategies:– Nugget First– S.A.R.: Situation, Action, Result
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Preparing for Behavioral Qs
• Create Preparation Grid for ProjectsOS Project Amazon Intern.
Enjoyed
Hated
Most Challenging
Hardest Bug
+ Behavioral Grid [for PM & less tech. roles]
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Structure 1: Nugget First
• Lead with your “thesis” / nugget– Grabs the listener’s attention– Gives them context for where you’re going.
A: I’m most proud of the way I re-architected the …
Q: What accomplishment are you most proud of?
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Structure 2: S.A.R.
ituationctionesult
SAR
What was the issue?
What did you do about it?
What was the impact?
Technical SkillsInterview Prep
McDowell | CareerCup.com
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
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
Technical SkillsBehavioralApplying
Process
Data Structures
• How to implement• When to use (pros / cons)
Linked Lists Stacks Queues
Trees Tries Graphs
Vectors Heaps Hashtables
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Algorithms
• Implementation• Space vs. Time
ComplexityQuick Sort Merge Sort
Tree Insert / Find Binary Search
Breadth-First Search
Depth-First Search
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Concepts
• Not just a concept – know how to code!
Threading System Design & Scalability
MemoryManagement
Recursion Probability + Combinatorics Bit Manipulation
Technical SkillsMastering the Interview
McDowell | CareerCup.com
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Technical Questions
1. Ask Questions!– Questions are more ambiguous than they appear
2. Talk out loud– Show us how you think
3. Think critically– Does your algorithm really work? What’s the space
and time complexity?
4. Code slowly and methodically– It’s not a race
5. Test your code– And make CAREFUL fixes.
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
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
Technical SkillsBehavioralApplying
Process
Types of Interview Questions
Coding & Algorithms
Object Oriented Design System Design
“Reverse a Linked List”
“Design a Parking Lot”
“Design a Web Crawler”
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Types of Interview QuestionsCoding & Algorithms
Pattern Matching
Simplify & Generalize
Base Case & Build
Data Structure Brainstorm
Object Orient
ed Design
System
Design
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
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.
Coding & Algorithms
Pattern Matching
Simplify & Generalize
Base Case & Build
Data Structure Brainstorm
Object Orient
ed Design
System
Design
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Algorithm Qs: Simplify & GeneralizeCoding & Algorithms
Pattern Matching
Simplify & Generalize
Base Case & Build
Data Structure Brainstorm
Object Orient
ed Design
System
Design
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
Technical SkillsBehavioralApplying
Process
Algorithm Qs: Base Case & BuildCoding & Algorithms
Pattern Matching
Simplify & Generalize
Base Case & Build
Data Structure Brainstorm
Object Orient
ed Design
System
Design
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
Technical SkillsBehavioralApplying
Process
Algorithm Qs: Data Structure BrainstormCoding & Algorithms
Pattern Matching
Simplify & Generalize
Base Case & Build
Data Structure Brainstorm
Object Orient
ed Design
System
Design
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
Technical SkillsBehavioralApplying
Process
Coding & Algorithms
Pattern Matching
Simplify & Generalize
Base Case & Build
Data Structure Brainstorm
Object Orient
ed Design
System
Design
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
Technical SkillsBehavioralApplying
Process
Object Oriented Design
Handle AmbiguityWhat about the question is ambiguous?
Design the Core ObjectsWhat are the main objects in the system?
Analyze RelationshipsHow are the objects related to each other?
Investigate ActionsWhat are the main operations?
Coding & Algorithms
Object Oriented Design System Design
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Coding & Algorithms
Object Oriented Design System Design
Object Oriented Design
Handle AmbiguityIs it a single restaurant, or part of a chain?
Design the Core ObjectsGuest, Party, Table, Server, Host, …
Analyze RelationshipsServer and Host are both Employees…
Investigate ActionsA Party is seated at a Table by a Host…
How would you design the data structures and objects for a restaurant?
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
System Design
Handle AmbiguityWhat about the question is ambiguous?
Make BelievePretend there wasn’t so much data & solve
Get RealGo back to the real problem. What breaks?
Solve ProblemsSolve the issues you just found.
Coding & Algorithms
Object Oriented Design System Design
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
System Design
Handle AmbiguityDo the words need to be in a specific order?
Make BelieveAssume everything can fit on one machine.
Get RealMust split up data across machines.
Solve ProblemsDivide hash table by file or by keyword?
Given millions of documents, find all documents
which contain a list of words.
Coding & Algorithms
Object Oriented Design System Design
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
Whew! All Done!
<Gulp> This is a lot of stuff. Do I need to get
everything right?
Coding & Algorithms
Pattern Matching
Simplify & Generalize
Base Case & Build
Data Structure Brainstorm
Object Orient
ed Design
System
Design
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
<Gulp> This is a lot of stuff. Do I need to get
everything right?
</Gulp>
Evaluation is RELATIVE, not absolute.
… it’s about how quickly you solved it relative to
other candidates.
It’s not about how quickly you solved the problem…
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
So RELAX!Interviews are supposed to be hard!
Everyone makes mistakes. Everyone!
Final Thoughts
McDowell | CareerCup.com
McDowell | CareerCup.com
Technical SkillsBehavioralApplying
Process
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
Technical SkillsBehavioralApplying
Process
Other ResourcesSold TodaySigned (just ask!)
CareerCup.com• Interview Videos• iPhone App• Resume Review• Mock Interviews
today
Rs. 400
5 stars!
Or, stalk me online at…• twitter.com/gayle• facebook.com/gayle• technologywoman.com• [email protected]