A* Search
Cannot implement Perfect Info!
Try to get best combination
use g(n) : best path cost so far
use heuristic h(n), as do not have the true hT(n)
A* Search is
BestFS( g + h )
That is, define   f(n) = g(n) + h(n)
estimated minimum cost via n
and use BestFS( f(n) )