Big-O 而不是 Little-O 意味着 Theta?同样,Big-Omega 而不是 little-Omega 意味着 Theta?

Big-O and not Little-O implies Theta? Similarly, Big-Omega and not little-Omega implies Theta?

如果f(n) is O(g(n))而不是o(g(n)),那么f(n) is theta(g(n))是真的吗?

类似地,f(n) is Omega(g(n)) 而不是 omega(g(n)) 意味着 f(n) is theta(g(n))

如果没有,你能提供一个explanation/counter-example吗?

*注意:将 O 视为 <=,将 o 视为 <.

If f(n) is O(g(n)) but not o(g(n)), is it true that f(n) is theta(g(n))?

是的,f(n) ∈ Θ(g(n)).

f(n) = O(g(n)) means f(n) ≤ Cg(n). 

f(n) = o(g(n)) is possible if and only if f(n) = O(g(n)), but f(n) ≠ Θ(g(n)).

因此,由于 f(n) 不是 o(g(n)),而是 O(g(n)),因此,f(n) ∈ Θ(g(n))。


*注意:将 Ω 视为 >=,将 ω 视为 >.

Similarly, f(n) is Omega(g(n)) but not omega(g(n)) implies f(n) is theta(g(n)).

是的,f(n) ∈ Θ(g(n))。遵循类似的逻辑:

f(n) = Ω(g(n)) means f(n) ≥ cg(n).

f(n) = ω(g(n)) is possible if and only if f(n) = Ω(g(n)), but f(n) ≠ Θ(g(n)).

因此,由于 f(n) 不是 ω(g(n)),而是 Ω(g(n)),因此,f(n) ∈ Θ(g(n))。