BFS A H 12 A B 1 B C 1 C D 1 A E 10 E F 2 F G 3 G H 3 A I 1 I J 1 J K 1 K L 1 L H 1 12 A 1 B 1 C 1 D 1 E 1 F 1 G 1 H 1 I 1 J 1 K 1 L 1