That's a different problem than the one we used. We added some additional complexity that required a search of the entire solution space to get a provably optimal answer, and then we made the maps & allowed # of moves large enough that brute force was impossible. So people had to build sub-optimal search solutions that pruned in intelligent ways.

Is the problem (statement, input and hopefully leaderboard) available online somewhere?

I figure it hasn't been used for recruiting in a long time, so there shouldn't be any downside of that nature to it being so. But there is the invested time in making it available, of course.

I hardly think I would be the only one thriled to try it just for fun. It would probably provide a great deal of goodwill for you guys, as well as further the industry's understanding of what constitutes a good take-home problem.

Did anyone use a SAT solver?

I took a quick look at it just now myself - it looks like it'd be pretty straightforward to solve by just brute-forcing every possible solution. Or is there some tortoise-hare type of "trick" I'm supposed to come up with?

The firebase problem states that there is no optimal solution. so it can be as easy as increasing the size of the gold mine in a way that a brute force solution it's not posible and you must find sub optimal maximums applying heuristics. The travelling salesman problem has a lot of literature to understand this kinds of problems that are usually some variations of this problem originally stated near 200 years ago.