"Asymptotic notation" is used to express "asymptotically complex degree".
1. Asymptotic notation includes:
(1) Theta (theta): tight bounds. Equivalent to "="
(2) O (Greater Europe): upper bound. The equivalent of "<="
(3) O (Theo): not tight upper bound. Equivalent to "<"
(4) Ω (large Omega): Lower bound. The equivalent of ">="
(5) Ω (small Omega): not a tight lower bound. Equivalent to ">"
Give the definition of these tokens:
Note: asymptotic nonnegative means "when n tends to infinity, f (n) and g (n) are nonnegative".
2. Use set theory to denote the relationship between these 5 symbols:
As you can see from the diagram above:
(1) if f (n) =θ (g (n)), then f (n) =o (g (n)) and f (n) =ω (g (n)).
(2) if f (n) = O (g (n)), then f (n) =o (g (n)).
(3) if f (n) =ω (g (n)), then f (n) =ω (g (n)).
Therefore, the most accurate use of these asymptotic notation should be "f (n) ∈o (g (n))", but it is generally written as "F (n) =o (g (n))".
Give some examples:
O (n^2) can be n,2n,1,2n^2 and so on.
Θ (n^2) can be n^2,3n^2 and so on.
Ω (n^2) can be n^3,n^10, but not n^2.
Ω (n^2) can be n^2,n^3,n^10 and so on.
O (n^2) can be n,1,3n, but not n^2.
3. To judge the asymptotic relationship of two functions
Here we have a very common method called "limit Method".
Seeing the above method, a lot of people will ask "why not O and ω." , because if f (n) =o (g (n)) is either f (n) = O (g (n)), or F (n) =θ (g (n)).
4. Relevant laws
5. Commonly used function order
The following is a list of functional classifications that are common when analyzing algorithms. All of these functions are on the verge of infinity, and the slower-growing functions are listed above. is an arbitrary constant.
Symbol |
Name |
|
Constant (order, same below) |
|
Logarithmic |
|
Multiple logarithm |
|
Linear, sub Linear |
|
is the iterated logarithm |
|
Linear logarithm, or logarithmic linear, quasi-linear, hyper-linear |
|
Square |
|
Polynomial, sometimes called "algebra" (order) |
|
Exponent, sometimes called "geometry" (order) |
|
Factorial, sometimes called "combination" (order) |