Cracking the Coding Interview

Cracking the Coding Interview
Gayle Laakmann McDowell
Strategies to Prepare for and Crack the Programming Interview
10/11/20
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Hi! I’m Gayle LaakmannMcDowell
gayle.com | twitter.com/gayle | facebook.com/gayle 10/11/2014
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(CS) (MBA)
<dev> </dev>
Author Interview Coach Interview Consulting

The Perfect Candidate
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Does the “perfect” candidate really exist?
… Yes. Many. Lots.
BUT! Many successful candidates aren’t perfect!

TODAY’S AGENDA
How to become a more perfect dev candidate

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How to Become a More

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•Coursera
•Bootcamps
•Read lots.
•Write lots.

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• Hackathons
• Diversity languages.
• Independent projects.

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• Startups
• Start your own

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• Length:
• 1 – 2 pages.
• 1 – 2 lines per bullet.
• 3 – 6 bullets per company.
• Projects.
• Clear accomplishments.
• Technical…
• But not overwhelming.
CareerCup.com/Resume

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THE SOFT SQUISHY STUFF
aka Behavioral Questions
great bang for your buck

The Pitch / Resume Walk-Through
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Your Past Work/Projects
• Prep 1 – 2 projects
• Hard/Cool
• You = Central
• Technical Depth
• All past work (esp. last job)
• Challenges, design/architecture, tradeoffs,
mistakes, successes, motivations
• What did YOU do? 16

Technical Questions
Why why why why why why why why meeeee
It happens for a reason.

What Really Happens
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What Really Happens
• Knowledge Questions
• Design/Scalability (+ coding)
• Problem Solving (+ coding)
• Coding
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Knowledge Questions
“What is a static class in Java?”
Trivia, Details, etc.

Knowledge Questions
• Know your stuff.
• Be cautious about what you list.
• If you don’t know, admit it.
• Derive it if possible.
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“Design Google Maps”
System Design
Complex Real-World Problems

Scalability/Design
W
W
Y
D
A
W 23

Scalability/Design
What
Would
You
Do
At
Work 24

Scalability/Design
• Scope the problem
• Ask questions
• Figure out biggest components
• Discuss tradeoffs
• Think about challenges/bottlenecks
• TEAMWORK!
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Problem Solving / Algorithm Questions
Why why why why why why why why meeeee
It happens for a reason.

Why?
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Why?
• Strong foundation in CS
• Analytic skills/intelligence.
• Ability to make tradeoffs.
• Discussion/teamwork ability.
• How you think about a problem.
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How You Are Judged
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How did you do RELATIVE
to other candidates on
the SAME question?

Essential Knowledge
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Data Structures Algorithms Concepts
Arrays / ArrayLists Merge Sort Big O (Time &
Space)
Hash Tables Quick Sort Recursion
Trees (+ Tries) Breadth-First
Search
Memoization /
Dynamic
Programming
Graphs Depth-First Search
Stacks / Queues Binary Search
Heaps

Preparation
• Implement DS/Algorithms
• MASTER Big O
• Practice with interview questions
• Code on paper/whiteboard
• Mock interviews
PUSH YOURSELF! 31

Solving a Problem Solving Question
How to… attempt to nail a question in 7 easy[ish] steps
There’s a method to the madness.

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CrackingTheCodingInterview.com
“Resources”

0. TALK
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1. Listen
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2. Example
BIG ENOUGH
+
GENERAL PURPOSE
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Ex: Intersection of 2 Sorted Distinct Arrays
[1, 12, 15, 19]
[2, 12, 13, 20]
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Too small

[1, 12, 15, 19, 20, 21]
[2, 12, 13, 17, 18, 25]
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Special case
|A| = |B|

[1, 12, 15, 19, 20, 21]
[2, 12, 13, 17, 18, 25, 27]
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Special case
One element in common

[1, 12, 15, 19, 20, 21]
[2, 12, 13, 19, 18, 25, 27]
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Special case
Common elements at same index

[1, 12, 15, 19, 20, 21]
[2, 15, 17, 19, 21, 25, 27]
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Good enough.

3. Brute Force
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4. Optimize
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Walk
through
brute force
Look for
optimizations
(BUD!)

4. Optimize… BUD?
Bottlenecks
Unnecessary work
Duplicated work
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[1, 12, 15, 19, 20, 21]
[2, 15, 17, 19, 21, 25, 27]
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Bottleneck: searching

Ex: a3 + b3 = c3 + d3
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Unnecessary work:
looking for d

Ex: a3 + b3 = c3 + d3
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Unnecessary work:
looking for d

Ex: a3 + b3 = c3 + d3
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Duplicated work:
c, d pairs over and over

Ex: a3 + b3 = c3 + d3
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Duplicated work:

Ex: a3 + b3 = c3 + d3
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Duplicated work:

MORE! MORE!
• BUD
• Space/time tradeoff
• Precompute / cache
• Hash tables
• Other DS: heaps, trees, stacks
PUSH YOURSELF! 51

5. Walk Through
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5. Walk Through
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Know the variables
And when they change

6. Write BEAUTIFUL code
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6. Write BEAUTIFUL code
•Well modularized
• Error cases (at least with TODOs)
• Clean and neat
• Good variables
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6. Modularized code
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7. Testing
1. Conceptual - does it make sense?
2. Weird stuff (x = len – 2)
3. Hot spots (end of list)
4. Small test cases
5. Special test cases
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How You Are Judged
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How did you do RELATIVE
to other candidates on
the SAME question?

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So RELAX!
Interviews are supposed to be hard!
Everyone makes mistakes.
Everyone!

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Talk to your interviewer
Be a great engineer.

More Resources
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CareerCup.com
• Interview Videos
• Resume Review
• Mock Interviews
• Consulting
Or, follow me online at…
• twitter.com/gayle
• facebook.com/gayle
• gayle.com
• gayle@gayle.com
• quora.com

Cracking the Coding Interview

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