Interview Prep - Algorithms

Resources for preparing for the algorithm portion of Front End job interviews.

Approach to solution finding

Treat the interview as if it was a collaboration session, and walk through as if you were solving the problem at work. Most importantly talk it out and let the interviewer know your thought process. Use these steps.

• Understand the question
• Identify test cases/conditions
• Design the solution
• Implement the solution
• Review the solution

Understand the question

Make sure you are in sync with the interviewer on the expectations. Verify any assumptions you may have.

• What is the expected behavior
• What are the inputs? (data structure, units, etc.)
• What are the outputs?
• Any special considerations (should the algorithm be stable?)
• If you don't know the formula or definition of a term, ask.
• Constraints

Identify test cases/conditions

Depending on the question, consider the standard case as well as boundary cases.

• Failure cases - Where the expected solution doesn't exist
• Variety - wildly varying values or all values are the same
• Number of elements - small or very large set
• Null conditions
• Duplicate conditions
• Boundary conditions

Design the solution

Sketch out the design. If you know there is a more elegant solution, but you only know how to do the brute force approach, acknowledge that.

• Observations - Any observations, (e.g. At most one letter can exist an odd number of times in a palindrome)
• Algorithm - Be able to describe the algorithm in steps
• Code - Sketch out the solution in pseudo code.
• Complexity - Be able to describe the complexity of your solution.
• Consider alternatives - Describe why you are rejecting a certain approach.
• What data structures will be used.

Implement the solution

• Write the solution
• Let the interview know of any utility methods that you don't feel need to be coded (e.g. swap)

Review the solution

• Walk through the solution with a test case showing intermediate output. Walking through, you may have an idea for an improvement or may identify an error. Share these with the interviewer.

• Address qualities

  • Performance
  • Efficiency
  • Scalability
  • Extensibility
  • Complexity
  • Memory usage
  • Potential improvements

Coaching:

• [Interview Kickstart] (http://interviewkickstart.com/) - SF Bay classes focused on the technical interview. Founded by Soham Mehta, one of the first five engineers at Box.
• [Career Cup] (http://www.careercup.com/interview) - $150+/hour mock interviews
• [Interview Coaching] (http://www.impactinterview.com/) - Coaching in cities around the country.
• [Interview Academy] (http://www.interviewacademy.io/) - 4 week course in Mountain view, CA.
  Founded by a Google employee
• Tutor Universe – Tutors - Not specifically interview oriented.
• Code Mendor - Mentors, hourly or long term. Not specifically interview oriented.

Mock Interviews:

• Skillbrush - Schedule an online mock interview with an expert
• Pramp - Peer to Peer online mock interviews

References:

• [Google Candidate Coaching Hangout - Video] (https://www.youtube.com/watch?v=oWbUtlUhwa8) Take special note at time 13:00 - discussion of how to approach underspecified problems.
• [Algorithm Design Canvas] (http://www.hiredintech.com/algorithm-design/the-algorithm-design-canvas) - Tech recruiter site with many helpful resources
• Technical Interview Cheat Sheet
• Sorting Algorithms Animations
• Interview Prep Wiki - Review Sheets
• Data Structures Visualizations
• Visualizing Algorithms
• DZone Refcardz – summary cheat sheets for dozens of languages

Books - Tech Interviews

• [Elements of Programming Interviews] (http://www.amazon.com/Elements-Programming-Interviews-Insiders-Guide/dp/1479274836)
  • Elements of Programming Interviews - [Solutions] (http://elementsofprogramminginterviews.com/solutions/)
• [Cracking the Coding Interview] (http://www.amazon.com/Cracking-Coding-Interview-Programming-Questions/dp/098478280X/ref=zg_bs_2578_1)
• [Programming Interviews Exposed] (http://www.amazon.com/Programming-Interviews-Exposed-Secrets-Programmer/dp/047012167X)

Books - Algorithms

• [Introduction to Algorithms] (http://www.amazon.com/Introduction-Algorithms-3rd-Thomas-Cormen/dp/0262033844/ref=sr_1_1?ie=UTF8&qid=1424027412&sr=8-1&keywords=algorithm) - by by Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, Clifford Stein - 31 July, 2011 - Addison Wesley
• [Algorithms - 4th Edition ] (http://www.amazon.com/Algorithms-4th-Robert-Sedgewick/dp/032157351X/ref=sr_1_1?s=books&ie=UTF8&qid=1424027540&sr=1-1) - - by Robert Sedgewick, Kevin Wayne - 19 March, 2011 - MIT Press
• [Algorithms in a Nutshell] (http://www.amazon.com/Algorithms-Nutshell-OReilly-George-Heineman-ebook/dp/B0043D2EGI/ref=sr_1_1?s=books&ie=UTF8&qid=1424027824&sr=1-1&keywords=algorithms+in+a+nutshell) - by George T. Heineman and Stanley Selkow - 30 june, 2009 - O'Reilly
• Algoirthm Design Manual - by Steven S. Skiena - 2nd Edition - 2008, Springer
  • Algorithm Design Manual - PDF Version
  • Alogirthm Design Manual - Website

Online practice:

• [Hacker Rank] (https://www.hackerrank.com/)
• Code Eval – Company linked challenges
• [Geeks for Geeks] (http://www.geeksforgeeks.org/) - Excellent collection of algorithm concepts, quizzes, and experiences at a variety of tech companies
• [Code Chef] (http://www.codechef.com/)
• [Top Coder] (http://www.topcoder.com/) - Download Arena for the practice room
• [PairUpToCode Exercises] (http://www.pairuptocode.com/) - Small set of HTML, Javascript exercises
• [JS Assessment] (https://github.com/rmurphey/js-assessment) - Github respository of javascript programs with failing/incomplete tests.
• [Project Euler] (https://projecteuler.net/) - An enormous number of problems to solve. Write the code, submit the answer, repeat.
• [Interview Cake] (https://www.interviewcake.com/) - Problems posted online or delivered weekly to your email.
• Coding Bad – Interactive java and python problems
• Leet Code – Interactive coding in a variety of languages
• Code Wars – Similar to hacker rank

Example questions posted by interviewees

• [Crazy for Code] (http://www.crazyforcode.com/interview-experiences/)
• [Glass Door - Interviews] (http://www.glassdoor.com/Interview/index.htm)
• [Coder Career] (http://codercareer.blogspot.com/)

Complexity Analysis references

• [Big O Cheat Sheet] (http://bigocheatsheet.com/) - Big O complexities for basic algorithms and data structures
• MIT paper on Big O Notation - Short overview of Big O notation.

Papers

• MapReduce: Simplified Data Processing on Large Clusters - Jeffrey Dean and Sanjay Ghemawat
• Bigtable: A Distributed Storage System for Structured Data - Fay Chang, Jeffrey Dean, Sanjay Ghemawat, Wilson C. Hsieh, Deborah A. Wallach Mike Burrows, Tushar Chandra, Andrew Fikes, Robert E. Grube
• Finding a needle in Haystack: Facebook’s photo storage - Doug Beaver, Sanjeev Kumar, Harry C. Li, Jason Sobel, Peter Vajgel
• Amazon.com Recommendations Item-to-Item Collaborative Filtering - Greg Linden, Brent Smith, and Jeremy York • Amazon.com
• Distributed Caching with Memcached - Aug 01, 2004 By Brad Fitzpatrick

Videos

• Tim Roughgarden - Associate Computer Science Professor at Stanford
• Tushar Roy - Tushar walkt through different problem sets.
• Krispy Karim - Variety of you tube playlists on Dynamic Programming and other algorithms.

Visualizing Algorithms

• Algomation - Create algorithms in javascript with visualizations.
• Visual Go - Step through animations of common algorithms.