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THE TECHNICAL INTERVIEW REFACTORING

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WHY EVEN BOTHER? REFACTORING THAT IS

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MARK SIEMERS RUBYCONF 2018 THE HIGH COSTS OF BAD HIRING DECISIONS ▸ Time ▸ Money ▸ Resources ▸ Opportunity Cost ▸ Reputation ▸ Morale ▸ Technical Debt REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 THE HIGH COSTS OF BAD HIRING DECISIONS ▸ Time ▸ Money ▸ Resources ▸ Opportunity Cost ▸ Reputation ▸ Morale ▸ Technical Debt HOW MUCH IS IT COSTING YOU? REFACTORING THE TECHNICAL INTERVIEW

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IS ANYTHING WRONG?

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DO NEW CANDIDATES WRITE CODE DURING THEIR INTERVIEW? Joel Spolsky - The Joel Test (#11)

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MARK SIEMERS RUBYCONF 2018 ANY CODING QUESTION IS FINE, RIGHT? ▸ Find min (or max) in a list ▸ Implement reversing a string ▸ Implement a sorting algorithm ▸ FizzBuzz (not actually FizzBuzz, but any contrived algorithm) ▸ “Now can you do it recursively?” REFACTORING THE TECHNICAL INTERVIEW

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IN A CARPENTRY INTERVIEW… ASK ANY QUESTION

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MARK SIEMERS RUBYCONF 2018 EQUIVALENT CARPENTRY INTERVIEW QUESTIONS REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 EQUIVALENT CARPENTRY INTERVIEW QUESTIONS ▸ How do you build a drill? REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 EQUIVALENT CARPENTRY INTERVIEW QUESTIONS ▸ How do you build a drill? ▸ How do you build a circular saw? REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 EQUIVALENT CARPENTRY INTERVIEW QUESTIONS ▸ How do you build a drill? ▸ How do you build a circular saw? ▸ Imagine a structure where ▸ Every 3rd plank is birch ▸ Every 5th plank is maple ▸ If the plank is divisible by 3 and 5, it must be maple and birch ▸ how many maple/birch planks in a 3 story structure? REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 EQUIVALENT CARPENTRY INTERVIEW QUESTIONS ▸ How do you build a drill? ▸ How do you build a circular saw? ▸ Imagine a structure where ▸ Every 3rd plank is birch ▸ Every 5th plank is maple ▸ If the plank is divisible by 3 and 5, it must be maple and birch ▸ how many maple/birch planks in a 3 story structure? REFACTORING THE TECHNICAL INTERVIEW WTF???

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WHY???

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WHY??? DO YOU WANT ME TO USE THIS ON THE JOB?

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (CARPENTRY) ▸ Solved ▸ Building drills and circular saws was solved long ago ▸ Standardized ▸ These tools are trustworthy and widely available ▸ Trivial ▸ Last example is an arbitrary and trivial task REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) ▸ Solved REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) ▸ Solved ▸ Quicksort ~ 1959 (Pre-dates cordless electric drill by about 10 years) REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) ▸ Solved ▸ Quicksort ~ 1959 (Pre-dates cordless electric drill by about 10 years) ▸ Merge Sort ~ 1945 (The year World War II ended) REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) ▸ Solved ▸ Quicksort ~ 1959 (Pre-dates cordless electric drill by about 10 years) ▸ Merge Sort ~ 1945 (The year World War II ended) ▸ Radix Sort ~ 1887 (About 35 years before the electric circular saw) REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) ▸ Solved ▸ Quicksort ~ 1959 (Pre-dates cordless electric drill by about 10 years) ▸ Merge Sort ~ 1945 (The year World War II ended) ▸ Radix Sort ~ 1887 (About 35 years before the electric circular saw) ▸ Standardized REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) ▸ Solved ▸ Quicksort ~ 1959 (Pre-dates cordless electric drill by about 10 years) ▸ Merge Sort ~ 1945 (The year World War II ended) ▸ Radix Sort ~ 1887 (About 35 years before the electric circular saw) ▸ Standardized ▸ What language or library doesn’t have sort, max, min, reverse, etc. built in? REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) ▸ Solved ▸ Quicksort ~ 1959 (Pre-dates cordless electric drill by about 10 years) ▸ Merge Sort ~ 1945 (The year World War II ended) ▸ Radix Sort ~ 1887 (About 35 years before the electric circular saw) ▸ Standardized ▸ What language or library doesn’t have sort, max, min, reverse, etc. built in? ▸ Studied REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) ▸ Solved ▸ Quicksort ~ 1959 (Pre-dates cordless electric drill by about 10 years) ▸ Merge Sort ~ 1945 (The year World War II ended) ▸ Radix Sort ~ 1887 (About 35 years before the electric circular saw) ▸ Standardized ▸ What language or library doesn’t have sort, max, min, reverse, etc. built in? ▸ Studied ▸ Hundreds of publications dedicated to the coding interview REFACTORING THE TECHNICAL INTERVIEW

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MARK SIEMERS RUBYCONF 2018 ISSUES WITH THESE QUESTIONS (SOFTWARE DEVELOPMENT) ▸ Solved ▸ Quicksort ~ 1959 (Pre-dates cordless electric drill by about 10 years) ▸ Merge Sort ~ 1945 (The year World War II ended) ▸ Radix Sort ~ 1887 (About 35 years before the electric circular saw) ▸ Standardized ▸ What language or library doesn’t have sort, max, min, reverse, etc. built in? ▸ Studied ▸ Hundreds of publications dedicated to the coding interview ▸ Trivial (FizzBuzz, Bubble Sort, etc.) REFACTORING THE TECHNICAL INTERVIEW

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WHY DO WE ASK THESE QUESTIONS?

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I’M NOT SURE…

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW OPTIMAL FOR ▸ Algorithm Writers ▸ Procedure Implementers

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW OPTIMAL FOR ▸ Object Architects ▸ System Designers ▸ Application Developers ▸ Many, many other roles NOT OPTIMAL FOR ▸ Algorithm Writers ▸ Procedure Implementers

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW While the skills on the left are valuable, Often, the skills on the right are more valuable. OPTIMAL FOR ▸ Object Architects ▸ System Designers ▸ Application Developers ▸ Many, many other roles NOT OPTIMAL FOR ▸ Algorithm Writers ▸ Procedure Implementers

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW TWO QUESTION LITMUS TEST FOR YOUR INTERVIEW

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW TWO QUESTION LITMUS TEST FOR YOUR INTERVIEW ▸ Would you be happy or upset/confused if someone did this on the job? ▸ What if someone actually implemented bubble sort on the job? FizzBuzz?

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW TWO QUESTION LITMUS TEST FOR YOUR INTERVIEW ▸ Would you be happy or upset/confused if someone did this on the job? ▸ What if someone actually implemented bubble sort on the job? FizzBuzz? ▸ Which book would best prepare someone for your interview …

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THIS ONE?

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THIS ONE? OR THIS ONE?

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ANSWERED YES TO EITHER QUESTION?

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ANSWERED YES TO EITHER QUESTION? CONSIDER A SLIGHTLY DIFFERENT APPROACH.

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WHAT IF I STILL NEED AN ALGORITHM WRITER?

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WHAT IF I STILL NEED AN ALGORITHM WRITER? OR I’M NOT SURE OF THE RIGHT BALANCE?

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WHAT IS THE POINT OF AN INTERVIEW?

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WHAT IS THE POINT OF AN INTERVIEW? TO SEE IF SOMEONE CAN DO THE JOB

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW JOB EXPECTATIONS

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW ▸ Read Code JOB EXPECTATIONS

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW ▸ Read Code ▸ Understand It JOB EXPECTATIONS

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW ▸ Read Code ▸ Understand It ▸ Make it better JOB EXPECTATIONS

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW ▸ Read Code ▸ Understand It ▸ Make it better JOB EXPECTATIONS JOB INTERVIEW EXPECTATIONS

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW ▸ Read Code ▸ Understand It ▸ Make it better ▸ Read Code JOB EXPECTATIONS JOB INTERVIEW EXPECTATIONS

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW ▸ Read Code ▸ Understand It ▸ Make it better ▸ Read Code ▸ Explain It JOB EXPECTATIONS JOB INTERVIEW EXPECTATIONS

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW ▸ Read Code ▸ Understand It ▸ Make it better ▸ Read Code ▸ Explain It ▸ Make it better JOB EXPECTATIONS JOB INTERVIEW EXPECTATIONS

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW ▸ Read Code ▸ Understand It ▸ Make it better ▸ Read Code ▸ Explain It ▸ Make it better JOB EXPECTATIONS JOB INTERVIEW EXPECTATIONS What about writing new code?

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“IT’S HARDER TO READ CODE THAN TO WRITE IT.” Joel Spolsky, A Fundamental Law of Programming

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“CODE IS READ MANY MORE TIMES THAN IT IS WRITTEN.” Sandi Metz

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"THE RATIO OF TIME SPENT READING VERSUS WRITING IS WELL OVER 10 TO 1.” Robert C. Martin, Clean Code

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW READING CODE VS WRITING CODE

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW READING CODE VS WRITING CODE ▸ Do you want to ask about the part of the job that is: ▸ 90% of the technical work and more difficult ▸ 10% of the technical work and easier

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW READING CODE VS WRITING CODE ▸ Do you want to ask about the part of the job that is: ▸ 90% of the technical work and more difficult ▸ 10% of the technical work and easier ▸ Even with “new” code on the job, do you expect: ▸ Starting from scratch without referencing any other code? ▸ Referencing examples and applying them to the problem at hand?

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GREAT, BUT WHAT CODE SHOULD THEY READ?

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GREAT, BUT WHAT CODE SHOULD THEY READ? YOURS

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LET’S TRY IT.

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READ CODE. EXPLAIN IT. MAKE IT BETTER.

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READ CODE. EXPLAIN IT. MAKE IT BETTER. WHAT IS THIS CODE DOING?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. ‘ORDER’ AND ‘SORT_BY’ - IS THERE A DIFFERENCE?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. WHY THE TERNARY?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. WHY THE ‘TO_S’? WHY THE ‘TO_I’

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW EXPLAINING CODE - REVIEW

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW EXPLAINING CODE - REVIEW ▸ What is the code doing? ▸ Learn how they translate code into human understanding

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW EXPLAINING CODE - REVIEW ▸ What is the code doing? ▸ Learn how they translate code into human understanding ▸ Explain the differences between ‘order’ and ‘sort_by’ ▸ Depth of knowledge of tools used on the job ▸ Do they consider tradeoffs and the potential for breaking things

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW EXPLAINING CODE - REVIEW ▸ What is the code doing? ▸ Learn how they translate code into human understanding ▸ Explain the differences between ‘order’ and ‘sort_by’ ▸ Depth of knowledge of tools used on the job ▸ Do they consider tradeoffs and the potential for breaking things ▸ Why the ternary? Why the ‘to_s’? ▸ Knowledge of the language’s treatment of operations on different types

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READ CODE. EXPLAIN IT. MAKE IT BETTER. HAS THIS IMPROVED?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. HAS THIS IMPROVED? IS IT MORE READABLE?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. HAS THIS IMPROVED?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. WHAT MAKES THIS A NAIVE SOLUTION? HAS THIS IMPROVED?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. HAS THIS IMPROVED?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. ANY ISSUES WITH THIS SOLUTION? HAS THIS IMPROVED?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. HAS THIS IMPROVED?

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READ CODE. EXPLAIN IT. MAKE IT BETTER. ANY ISSUES WITH THIS SOLUTION? HAS THIS IMPROVED?

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW RECAP OF FIRST EXAMPLE - DID THEY ASK GOOD QUESTIONS

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW RECAP OF FIRST EXAMPLE - DID THEY ASK GOOD QUESTIONS ▸ About writing tests?

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW RECAP OF FIRST EXAMPLE - DID THEY ASK GOOD QUESTIONS ▸ About writing tests? ▸ About the database? ▸ Foreign key constraints, Indexing, Postgres vs MySQL, etc.

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW RECAP OF FIRST EXAMPLE - DID THEY ASK GOOD QUESTIONS ▸ About writing tests? ▸ About the database? ▸ Foreign key constraints, Indexing, Postgres vs MySQL, etc. ▸ About Rails version and Ruby version

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW RECAP OF FIRST EXAMPLE - DID THEY ASK GOOD QUESTIONS ▸ About writing tests? ▸ About the database? ▸ Foreign key constraints, Indexing, Postgres vs MySQL, etc. ▸ About Rails version and Ruby version ▸ About commit messages or reasons behind the initial implementation?

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BUT DOES IT SCALE? Jeff Bezos - Philosophy on Life Also credited to every anonymous Ruby hater, ever.

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READ CODE. EXPLAIN IT. MAKE IT BETTER.

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READ CODE. EXPLAIN IT. MAKE IT BETTER. WHAT ARE SOME CONCERNS WITH THIS CODE? HOW DO WE MAKE IT BETTER?

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READ CODE. EXPLAIN IT. MAKE IT BETTER SMALLER. WHAT ABOUT A NEW OBJECT?

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READ CODE. EXPLAIN IT. MAKE IT BETTER SMALLER.

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MARK SIEMERS RUBYCONF 2018 CURATING YOUR OWN INTERVIEW QUESTIONS ▸ When doing a bug fix or code refactor, save a gist/snippet of before and after with notes ▸ Or search commit history ▸ Pull a ticket from your current sprint ▸ Run a churn vs complexity report or flog score REFACTORING THE TECHNICAL INTERVIEW

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Move this way

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WHAT IF MY CODE IS CONFIDENTIAL?

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WHAT IF MY CODE IS CONFIDENTIAL? USE OPEN SOURCE!

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MARK SIEMERS RUBYCONF 2018 REFACTORING THE TECHNICAL INTERVIEW USE OPEN SOURCE REPOSITORIES ▸ Use Open Source Repositories ▸ Ruby - 539k Repos ▸ Crystal - 908 Repos ▸ C - 197k Repos ▸ Python - 517k Repos ▸ C# - 173k Repos ▸ Elixir - 3k Repos ▸ JavaScript - 749k Repos ▸ Java - 753k Repos ▸ Objective-J - 443 Repos

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THANK YOU Mark Siemers Refactoring the Coding Interview [email protected]