Jan 30, 06 Add weights to egdes.
  Changes are made in "node.h", "pairs_parser.cpp"


Jan 12, 06 The search for the minimal set of node for shortest-path clusters
are not minimal spanning tree (because shortest-path cluster can have circles).
The shortest-path cluster is not exactly traveling salesman problem, because 
leaf nodes have to passed N-1 times. 

Dec  7, 05 Hong Qin decided to write a c++ version of Dijkastra's single source shortest-path algorithm. 
