+#include "sliding_tile_lib.h"
+
+signed char adjacent[BOARD_SIZE][5] = {
+ 1, 4, -1, -1, -1,
+ 0, 2, 5, -1, -1,
+ 1, 3, 6, -1, -1,
+ 2, 7, -1, -1, -1,
+ 0, 5, 8, -1, -1,
+ 1, 4, 6, 9, -1,
+ 2, 5, 7, 10, -1,
+ 3, 6, 11, -1, -1,
+ 4, 9, 12, -1, -1,
+ 5, 8, 10, 13, -1,
+ 6, 9, 11, 14, -1,
+ 7, 10, 15, -1, -1,
+ 8, 13, -1, -1, -1,
+ 9, 12, 14, -1, -1,
+ 10, 13, 15, -1, -1,
+ 11, 14, -1, -1, -1,
+};