Quicksort Algorithm in Objective-C

gistfile1.m

- (void)sortMyArray
{
    NSMutableArray *unsorted = [NSMutableArray arrayWithArray:@[@67, @1, @14, @22, @77, @23, @21, @17, @99, @107, @89, @20]];
    NSLog(@"Unsorted:");
    NSLog(@"%@",unsorted);
    
    NSMutableArray *sorted = [self quickSort:unsorted];
    NSLog(@"Sorted:");
    NSLog(@"%@",sorted);
}

- (NSMutableArray *)quickSort:(NSMutableArray *)unsortedArray
{
    NSMutableArray *lessThanArray = [NSMutableArray new];
    NSMutableArray *greaterThanArray = [NSMutableArray new];
    
    if (unsortedArray.count < 1) {
        return nil;
    }
    
    int randomPivotPoint = arc4random() % [unsortedArray count];
    NSNumber *pivot = unsortedArray[randomPivotPoint];
    [unsortedArray removeObjectAtIndex:randomPivotPoint];
    
    for (NSNumber *num in unsortedArray) {
        if (num < pivot) {
            [lessThanArray addObject:num];
        } else {
            [greaterThanArray addObject:num];
        }
    }
    
    NSMutableArray *sorted = [NSMutableArray new];
    [sorted addObjectsFromArray:[self quickSort:lessThanArray]];
    [sorted addObject:pivot];
    [sorted addObjectsFromArray:[self quickSort:greaterThanArray]];
    
    return sorted;
}