How to calculate order (big O) for more complex algorithms (eg quicksort)

Question

I know there are quite a bunch of questions about big O notation, I have already checked:

• Plain english explanation of Big O
• Big O, how do you calculate/a

Answer 1

You can usually claim log n for algorithms where it halves the space/time each time it runs. A good example of this is any binary algorithm (e.g., binary search). You pick either left or right, which then axes the space you're searching in half. The pattern of repeatedly doing half is log n.