Also should read this guy's Phd thesis http://eddrobinson.net

A comprehensive collection of algorithm implementations for over seventy of the most fundamental problems in combinatorial algorithms. The problem taxonomy, implementations, and supporting material are all drawn from my book The Algorithm Design Manual. Since the practical person is more often looking for a program than an algorithm, we provide pointers to solid implementations of useful algorithms, when they are available.

Algorithmatic.com aspires to serve as a global repository of algorithms from all fields, and as an easy-access environment for algorithm design and prototyping through Algorithmatic's programming language and in-browser IDE. Put simply, Algorithmatic.com is for algorithms what Wikipedia is for articles. Also, these algorithms are instantly executable from within the browser.

br = ( (avg_num_votes * avg_rating) + (this_num_votes * this_rating) ) / (avg_num_votes + this_num_votes)
where
* avg_num_votes: The average number of votes of all items that have num_votes>0
* avg_rating: The average rating of each item (again, of those that have num_votes>0)
* this_num_votes: number of votes for this item
* this_rating: the rating of this item

( n ) n! ( n + 1 ) n+1 ( n )
| | = ------------- can instead be written | | = ----- | |
( k ) k! ( n - k!)!