Code Practice

Interviews GitHub Repo from kdn251 - great collection of solutions to code challenges from Cracking The Coding Interview, LeetCode, as well as from select companies (Google, Facebook and Amazon, for example). Recommend that you attempt your solution first and then take a peek here.

CodeQuizzes - Beginner-friendly way to cover some topics before an interview, flashcard style. CS concepts are not that deep nor wide but it's great for checking more language specific quirks.

RegEx Crossword Who even knew that this existed. If you hate RegEx, this will give you nightmares, or could quite possibly give you a whole new appreciation for it. Check out the tutorials and challenges to help you overcome your fear of RegEx. Use Scriptular.com editor to test your JavaScript and Rubular.com for Ruby.

Chicago Tech Interviews

Practice Code Challenges

Firecode - Firecode judges your current level of algorithms knowledge and utilizes that to assign problems to stretch your knowledge. The difficulty of the problems slowly increases as you solve more problems and level up. It encourages you to review problems you've seen before and also includes hints for when you're stuck on a problem.

CodeFights - competing against a bot and earn coins that you can exchange for things! Great for beginners and those who love graphical interfaces. There's a study plan that focuses specifically on Interview Practice. Be sure to click on the topics button as they have a very nice overview of data structures, going over Big O. For example: Arrays.

Codility - Some tech companies have utilized Codility challenges so why not test them out yourself. Best of all, it's free!. Another good thing are the lessons that you can download (PDFs), breaking down concepts from basic loops to the complexity of a binary search algorithm.

HackerRank - You do need to read/parse the file before you even have something to work with, though. So be sure to do this exercise, first and bookmark, as not all challenges will include stdin/stdout code and then you'll be wondering forever, why your code is not passing or returns an error: Solve Me First. Bonus: Author of Cracking the Coding Interview, Gayle Laakmann McDowell, put together some videos for HackerRank, going over some of the problems from the book. Clear and to the point. HackerRank Cracking the Coding Interview Challenges

Leet Code - Wouldn't recommend for beginners just because there's not much structure to the challenges and the lessons that they have jump straight to Tree data structures. So much more geared towards Intermediate/Advanced. Computer Science topics expand beyond just Algorithms/Data Structures and into Object-Oriented Design, Operating Systems, Database, and System Design. Premium subscribers can select mock interviews specific to companies, like Google or Facebook. Otherwise, it's free if you just want the practice.

Exercism - there's some setup involved like installing the Command-Line Client, but there's a test suite included so you can practice Test-Driven Development and the command line. You can compare to other submissions and get feedback, and have different iterations of your code if you want to optimize its performance. And you'll have a local copy of your code.