Is Big Oh the only notation used to measure complexity in STL
<p>I have started reading C++ STL and also found a book for that!. while i was reading the complexity,which plays major role in choosing algorithms and data structures i have been seeing that the Big Oh notation was only used with different variables(O(n),O(log(n).,) and by further surfing i found
the Big Oh denotes <code>f(x) = O(g(x))--(big-oh) means that the growth rate of f(x) is asymptotically less than or equal to to the growth rate of g(x)</code></p>

<p>So my question is, if an algorithms time complexity always results equal to the growth of g(x), why we mention that complexity as <code>f(x)=O(n)[Big oh of n]</code> rather than using (theta), because when i read about (theta) that said <code>f(x) = Θ(g(x)) (theta) means that the growth rate of f(x) is asymptotically equal to the growth rate of g(x)</code></p>

<p>Here the notation possibly be (theta) instead of O(N) wasn't it? or any reason for using big oh.</p>

<p>And what notation should we use to measure the space complexity.i don't see anything talks about space complexity regard STL in that book.</p>

<p>reference: <a href="https://stackoverflow.com/questions/471199/what-is-the-difference-between-%CE%98n-and-on">What is the difference between Θ(n) and O(n)?</a></p>