Question

What is the complexity of -[NSArray insertObject:atIndex:] — N? or constant?

Also, how can I find out the complexity of various Objective-C statements?

Answer 1

There is a discussion here and CFArray.h source code states:

Computational Complexity
The access time for a value in the array is
guaranteed to be at worst O(lg N) for any implementation, current and
future, but will often be O(1) (constant time). Linear search
operations similarly have a worst case complexity of O(Nlg N),
though typically the bounds will be tighter, and so on. Insertion or
deletion operations will typically be linear in the number of values
in the array, but may be O(Nlg N) clearly in the worst case in some
implementations. There are no favored positions within the array for
performance; that is, it is not necessarily faster to access values
with low indices, or to insert or delete values with high indices, or
whatever.