# 資料結構

### Asymptotic Notation-Big "oh"

#### f(n) = O(g(n)) iff
$\exists$ positive const , $c$ and $n_{0}\ni$ $f(n)$ $\leq$ $cg(n)$ $n$,$n$ $\geq$ $n_{0}$

eg.
* $3n+2 = O(n)$       $3n+2 \leq 4n$ for all n $\geq$ 2

* $10n^{2}+4n+2=O(n^{2})$   $10n^{2}+4n+2$ $\leq$ 11$n^{2}$ for all n>=10

* $3n+2=O(n^{2})$        $3n+2 \leq n^{2}$ for all n>=4

$g(n)$ should be a least upper bound