A-star is used to find the shortest path between a startnode and an endnode in a graph. What algorithm is used to solve something were the target state isn't specifically known and we instead only have a criteria for the target state?
For example, can a sudoku puzzle be solved with an Astar-like algorithm? We dont know how the endstate will look like (which number is where) but we do know the rules of sudoku, a criteria for a winning state. Therefore I have a startnode and just a criteria for the endnode, which algorithm to use?
You dont have to know the exact target endstate. It all comes down to the heuristic function, when it returns 0 you could assume to have found (at least) one of the valid endstates.
So during the a*, instead of checking if current_node == target_node, check if current_node.h() returns 0. If so, it should be infinitely close and/or overlapping the goal/endstate.