h' (NODE). This means that NODE is not solvable. If there are successors then for each one
called SUCCESSOR, that is not also an ancester of NODE do the following
(a) add SUCCESSOR to graph G
set of nodes that have been marked SOLVED. Initialize S to NODE. Until S is empty repeat
the following procedure;
are have been labeled SOLVED.
be propagate backwards up the graph . hence all the ancestors of CURRENT are added