回复：2*4!可以理解，5!仍不太明白。anyway, thank you!

来源: 于 2010-04-17 05:43:11 [旧帖] [给我悄悄话] 本文已被阅读：次

We get a circle first and put 123456 on it.6 has to been connected 1 and/or 5 .If 5 between 1 and 5 OK,if out,as there four sections,two are OK two not OK.So,...