[schtog]

Several algorithms and techniques and operating system(s?).

[boju1]

http://en.wikipedia.org/wiki/Dijkstra%27s_algorithm

and

http://www.dgp.toronto.edu/people/JamesStewart/270/9798s/Laf...

I myself coded an implementation of this algorithm for a map itinerary project. It's powerful in my opiniom.