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Coding interview workshop notes


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Fannie Mitchell Expert in Residence, YJ Yang '15 presented on Coding Interview Strategies on campus in January 2016. These are notes from his presentation.

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Coding interview workshop notes

  1. 1. Career Center Fannie Mitchell Expert in Residence: Coding Interview Strategies for Success Adapted from YJ Yang, ’15 Campus Presentation January 27, 2016 What does a technical interview look like? • An actual engineer will interview you, not necessarily from the team you’re interviewing for • The following schedule applies for both phone and on-site: -Introduction Interviewer introduces self/team, interviewee introduce self, “What made you apply to this company/ position?” -1 or 2 coding challenges -“Any questions about us?” Advice: Introducing yourself • Before you start, offer them a hard copy of your resume, if on-site • Keep it short, get straight to the point -If you have a specific area of expertise, discuss how you’ve come to choose that area -If not, focus on the variety of engineering you’ve had experience with • Use this site to see what types of stacks (technology platforms/software, etc.) a company uses so you can talk about your own skills in relation to what they use Advice: Ask for Feedback At the end of every interview session (both phone and on-site), ask these three questions: • Do you have any feedback for me? Is there anything I could have done better? -This is particularly important at a company like Microsoft, where interviewers talk to one another before each session of your on-site interviews, so you can continue to improve throughout the day • What are the next steps? • Can I have your email address? (send a thank-you note immediately after your interview) Three categories of coding challenges Data Structures and Algorithms Unless you’re interviewing for a position that is really intensive on data structures and algorithm analysis, you can likely expect only a very small subset of what you learned in CS201 Data Structures -Linked lists The most popular interview question Prepare for problems where you have to use two cursors • Hash sets/maps -Know at least one naive implementation -Worst-case Big-O can get tricky - it is not O(1) • Trees -Know how to traverse a BST and why it is ideally O(log N) -It’s unlikely that you will be asked how to efficiently remove a node or about how a red- black tree works • Graphs: Know DFS vs BFS • Heaps: unlikely that you’ll encounter questions about this • Stacks, queues: unlikely that you’ll encounter questions about this Algorithms • You should be ready to do Big-O (both time and space) on your algo • Usually comes down to three types: -Brute force: O(N) -Divide and conquer: O(log N) or O(N log N) -Dynamic programming: O(M*N) or something like that DP is a surprisingly popular topic. But always keep in mind that DP is nothing more than just memoizing Duke Career Center • • 919-660-1050 • Bay 5, Smith Warehouse, 2nd Floor • 114 S. Buchanan Blvd., Box 90950, Durham, NC 27708
  2. 2. Algorithms, cont. • Sorting/searching algorithms you have to know -Binary search, quicksort, mergesort, bucket/ radix sort -You have to know how bucket/radix sort relates to the RAM -It’s unlikely you’ll encounter other algorithms • Platform-specific • e.g. What will the result of this JavaScript code be? • If you applied to a very specific position, you should expect these, for a general position at a large tech company, you won’t really be asked these • The best way to learn these is through experience • Advice: having an expertise in a specific platform as an undergrad will really broaden your options -Pick a field (if you’re not sure, iOS is in high demand), buy the bible-status book in that field and master it, then try a few projects and publish them on GitHub GitHub is a great way to show your skill and code that you’ve written -Read every single day to catch up on recent developments inside/outside your field Design • For software engineering positions, these questions have you sketch the big picture of how to implement an actually functioning software whole • Know roughly how to design the following: -Hangman solver -Minesweeper -Google AutoComplete -Raft consensus Three caveats of coding challenges • Whiteboard coding -In an on-site interview, you’ll most likely be writing actual computer code on a whiteboard with a marker -In a phone interview, you’ll be using a shared document like Google Docs -Typically, pseudocode is fine, language is your choice, and the code doesn’t have to be completely functional (except for with Google) -Try to completely silence your inner voice and speak everything out loud -If you find this difficult, one tip is to try breathing only through the mouth, not through the nose • Assumptions -Interviewers will intentionally give you problems with incomplete preconditions -e.g. Write a function that finds a phone number in a given string A question like this already has a number of traps. Be sure to ask questions like: What is a phone number? (e.g. Does it include dashes? How many numbers?) What is the given string encoded in? UTF-8? ASCII? -Whenever you are asked about something with strings, question them- there are often a lot of hidden traps in a question like this -Keep refining your preconditions until the interviewer asks you to move on • Testing -You should always offer to describe how you’d test your solution on a holistic level -Pro tip: the “60% unit / 30% integration / 10% user-agent” rule of thumb -Other types of testing: load, monkey, etc. - naughty-strings Duke Career Center • • 919-660-1050 • Bay 5, Smith Warehouse, 2nd Floor • 114 S. Buchanan Blvd., Box 90950, Durham, NC 27708