Question

What is the simplest way to do a binary search on an (already) sorted NSArray?

Some potential ways I have spotted so far include:

1. The use of CFArrayBSearchValues (mentioned here) – would this work on an NSArray?

2. The method indexOfObject:inSortedRange:options:usingComparator: of NSArray assumes the array is sorted and takes an opts param of type NSBinarySearchingOptions – does this mean it performs a binary search? The docs just say:

   Returns the index, within a specified range, of an object compared with elements in the array using a given NSComparator block.

3. Write my own binary search method (something along the lines of this).

I should add that I am programming for iOS 4.3+

Thanks in advance.

Answer 1

1 and 2 will both work. #2 is probably easier; it certainly doesn’t make sense for that method to do anything other than a binary search (if the range is above a certain size, say). You could verify on a large array that it only does a small number of comparisons.