compare two arrays and get the common items

I have two arrays, but they have different lengths. I want to compare these two arrays and put common items to a new array. meanwhile there should not be have duplicate items is the third array. I really mess up with this, please give me a help. highly thankful . . .

Something like this?

NSMutableSet* set1 = [NSMutableSet setWithArray:array1];
NSMutableSet* set2 = [NSMutableSet setWithArray:array2];
[set1 intersectSet:set2]; //this will give you only the objects that are in both sets

NSArray* result = [set1 allObjects];

This has the benefit of not looking up the objects in the array, while looping through another array, which has N^2 complexity and may take a while if the arrays are large.

Edit: set2 doesn't have to be mutable, might as well use just

NSSet* set2 = [NSSet setWithArray:array2];