[理工] Aysmptotic Notations題目

作者: x411066 (熱開水)   2020-01-05 16:24:13
您好,我想問的問題如下:
已知lg(n!) = Θ(n*lg n)
1. (lg n)! is not Polynomailly Bounded
lg(lg n)! = Θ(lg n * lg (lg n))
= Θ(lg n * lglg n)
= ω(lg n)
因為lg(lg n)! != O(lg n),所以(lg n)! 不是 Polynomail-Bounded
2. (lglg n)! is Polynomailly Bounded
lg(lglg n)! = Θ(lglg n * lg (lglg n))
= O((lglg n)^2)
= O(lg^2(lg n))
= O(lg n)
因為lg(lglg n)! = o(lg n),所以(lglg n)!是Polynomail-Bounded
Q: 關於1.中的敘述,lg(lg n)!是否可以取
log(log n)! = Θ(lg n * lglg n)
= O((lg n)^2) = O(lg^2 n)
然後就說明因為lg(f(n)) != O(lg n),所以f(n)不是Polynomail-Bounded?
還是說得要取little-omega,找到lg(f(n)) > ω(lgn),
才可以說明不是Polynomail-Bounded?
作者: MASAGA (和泉千晶我老婆)   2020-01-05 20:00:00
因為是bounded 所以不能取上界吧就像n=O(2^n) 但n還是polynomial

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