Best way to remove duplicate objects from multi dimension MutableArray objective-C

Question

I'm looking for the best solution to remove duplicate objects from multi dimension array in objective-C (Swift is also fine) from some array like this:

muliDemensionArray = @[
                                 @[@"1", @"2", @"3", @"4", @"4",],
                                 @[@"11", @"13", @"24", @"14",],
                                 @[@"1", @"3", @"24", @"21",],
                                 ];

Do we have any algorithm or solution from NSOrderedSet/NSMutableArray support us to do this without loop/ reduce loop as much as possible?

This is expected result to remove all duplicates across all arrays:

mutilDemensionArray = @[
                                 @[@"1", @"2", @"3", @"4",],
                                 @[@"11", @"13", @"24", @"14",],
                                 @[@"21",],
                                 ];

• If we have many duplicate object, so keep the first one and remove others.
• I don't care about the order of objects in sub arrays, just care about the order of the sub arrays.

Answer 1

You can use the property of NSSets that they will only store a single instance of a given value.

• First convert each sub-array into a set, that will remove duplicates that are in that array.

• Then, subtract the set of items that have already been seen.

• Convert the result back to an array and add it to your output array.

• Finally, add the items in that sub-array to the set of items that have already been seen.

Something like:

-(NSArray *)removeDuplicatesFromArray:(NSArray *)array {

    NSMutableArray *returnArray=[NSMutableArray new];
    NSMutableSet *cumulativeSet=[NSMutableSet new];

    for (NSArray *innerArray in array) { 
        NSMutableSet *innerSet = [NSMutableSet setWithArray:innerArray];
        [innerSet minusSet:cumulativeSet];
        [cumulativeSet unionSet:innerSet];

        [returnArray addObject:[innerSet allObjects]];
    }

    return [returnArray copy];
 }