A*解决八数码难题的Nilson

关于Nilsson sequence score这个估计花费算法（也就是计算h的，估计函数） 其中 Nilsson's sequence score A tile in the center scores 1 (since it should be empty) For each tile not in the center, if the tile clockwise to it is not the one that should be clockwise to it then score 2. Multiply this sequence by three and finally add the total distance you need to move each tile back to its correct position.