http://cooervo.github.io/Algorithms-DataStructures-BigONotation/index.html
http://www.cs.usfca.edu/~galles/visualization/Algorithms.html
http://stackoverflow.com/questions/487258/plain-english-explanation-of-big-o
https://wiki.python.org/moin/TimeComplexity
http://www.topcoder.com/community/data-science/data-science-tutorials/
