This, so much. I remember writing a solver for a different game, and already had a dead end check in it, but with increasing board size it took half an hour to

This, so much. I remember writing a solver for a different game, and already had a dead end check in it, but with increasing board size it took half an hour to find a solution. Then I added another check for a different dead end condition. This actually required quite a lot of additional work, more than doubling the time spent for evaluating each board state. But it brought down the time from 30 minutes to a fraction of a second!