Quora

http://www.quora.com/Algorithms/What-is-the-best-non-boring-way-to-learn-algorithms#

Search Algorithm

http://qiao.github.io/PathFinding.js/visual/

http://www.topcoder.com

http://heuristicswiki.wikispaces.com/IDA*

http://codeforces.com

http://www.codechef.com/problems/LEBALONS

http://www.ambesty.com/Content/Welcome/Prerequisite/prerequisite.aspx?sec=1


BigO Notation

A standard way to assess the efficiency of code.

Fastest to Slowest

1. O(1) -  Constant: input size n has no effect on execution time.
2. O(log(n)) - Log : When only part of the total input size is visited.
3. O(n) - Linear
4. O(n*log(n)) - Some items are visited more than once.
5. O(n^2) - Power
6. O(2^n) - Exponential: For every input that you give the size keeps on increasing and the total work multiplies