public class NShortestPaths
N-shortest paths operation.
See: M. Mohri, M. Riley,
"An Efficient Algorithm for the n-best-strings problem", Proceedings of the
International Conference on Spoken Language Processing 2002 (ICSLP '02).
See: M. Mohri,
"Semiring Framework and Algorithms for Shortest-Distance Problems", Journal
of Automata, Languages and Combinatorics, 7(3), pp. 321-350, 2002.