Here are some of the useful links:

Big-O Cheat Sheet Tech Interview Cheat Sheet Data Structures Cheat Sheet Data Structures Cheat Sheet Algorithmic Cheat Sheet Guide to selecting appropriate Map/Collection in Java Data Structures Checkout notes Data Structures and Algorithms with Object-Oriented Design Patterns in Java Data Structures Tutorial Notes Algorithms & Data Structures - Notes by cooervo Algorithm Wiki Visual Algo UB Data Structures in C++ Lecture Slides & Notes Skiena's DS & Algo Audio/Video/Slides Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne Nick Johnsonz's Blog : Damn Cool Algorithms Algorist Justin Wetherell: Data Structures & Algorithms implementation in Java Ashish Chopra: Data Structures implementation in Java Prakhar Srivastav: Data Structures implementation in Python Battistella Stefano : Data Structures implementation in Javascript Daniel Fu : Data Structures implementation in C++ More on reddit.com

The main thing Java developers ... API Javadoc. 2010-10-08T18:14:53.837Z+00:00 ... @Steve: thanks, not sure what you mean by Python's "boatload of invocation options and environmental variables" — generally things work fine by typing "python myprog.py" But in any case, the point of a cheat-sheet is to aid one's memory; most cheat-sheets presume the reader is already very comfortable with core concepts like control flow, reserved keywords, data structures, ... More on stackoverflow.com

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Good for people getting into programming in general. I only have one remark: I wouldn't qualify O(n) as "Slow !" since it's still practically fast for low values of n and has the elegance of scaling linearly, which is one of the best scenarios available in the vast amount of cases a programmer will face. More on reddit.com