You are close, but not exactly

Don't rush to judge the quality of the question. From my point of view, it is indeed a good question.

1. Although it is complicated, you can still use combinatorial and permutation. You just need to be careful.

2. The extension of question enter the realm of graph theory, which makes it more interesting, and heading toward broader applications.

所有跟帖： 

• 72=(5!-4!*2) -jinjing- ♀ (10 bytes) () 04/15/2010 postreply 13:26:38

• This seems to be the best solution, can you reveal details? -SwiperTheFox- ♂ (6 bytes) () 04/16/2010 postreply 09:44:10

• Thanks. -jinjing- ♀ (0 bytes) () 04/17/2010 postreply 05:17:39

• details? please! -皆兄弟也- ♂ (0 bytes) () 04/16/2010 postreply 12:19:17

• 回複：details? please! -jinjing- ♀ (221 bytes) () 04/16/2010 postreply 16:00:53

• 2*4!可以理解，5!仍不太明白。anyway, thank you! -皆兄弟也- ♂ (0 bytes) () 04/16/2010 postreply 20:55:59

• 回複：2*4!可以理解，5!仍不太明白。anyway, thank you! -jinjing- ♀ (161 bytes) () 04/17/2010 postreply 05:43:11