don't you think

来源: 于 2009-01-19 14:14:56 [博客] [旧帖] [给我悄悄话] 本文已被阅读：次

把n个球放在3个盒子中的2个有3*2^n种方法 should include the possibility that 把n个球放在3个盒子中的1个?