** Heuristic Search: A***

The A* algorithm uses both actual distance (as in Dijkstra's algorithm) and a heuristic estimate of the remaining distance. It is both very efficient and able to overcome local maxima.

A* chooses the next node based on * lowest
estimated total cost* of a path through the node.

Estimated Total Costf(n) = g(n) + h(n)

g(n)= Cost from Start ton[known]

h(n)= Cost fromnto Goal [estimated]

g(n) h(n)? Start -------> n -------> Goal

The * heuristic function*, * h *, estimates the cost of
getting from a given node n to the goal. If * h * is good,
the search will be highly directed and
efficient; for example, airline distance is an
excellent heuristic distance estimator for route
finding. If * h * is not so good or has pathologies,
inclusion of the known cost * g * keeps
the search from getting stuck or going too far astray.