don't you think

來源: 於 2009-01-19 14:14:56 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

把n個球放在3個盒子中的2個有3*2^n種方法 should include the possibility that 把n個球放在3個盒子中的1個?