Finding out NSArray/NSMutableArray changes' indices

Question

I have a NSMutableArray oldArray. Now, at one point, this NSMutableArray object gets updated with another NSMutableArray,

Answer 1

1. addedArray = newArray ∖ (newArray ∩ oldArray)

          = newArray ∖ ({@"a",@"c",@"d",@"e",@"f",@"h"} ∩ {@"a",@"b",@"d",@"e",@"g"}) 
          = newArray ∖ {@"a",@"d",@"e"}            
          = {@"a",@"c",@"d",@"e",@"f",@"h"} ∖ {@"a",@"d",@"e"}
          = {@"c",@"f",@"h"}             
   

2. removedArray = oldArray ∖ (oldArray ∩ newArray)

            = oldArray ∖ ({@"a",@"b",@"d",@"e",@"g"} ∩ {@"a",@"c",@"d",@"e",@"f",@"h"})
            = oldArray ∖ {@"a",@"d",@"e"}
            = {@"a",@"b",@"d",@"e",@"g"} ∖ {@"a",@"d",@"e"}
            = {@"b",@"g"}
   

To find intersections of array, you can view the following SO post: Finding Intersection of NSMutableArrays