How to Find Duplicate Values in Arrays?

Question

I am working on SQLite and I have written a query which returns me two arrays ItemsArray and CustomersIDArray as:

ItemsArray
Element at Index 0 = Off White,
Element at Index 1 = Fan,
Element at Index 2 = Off White,
Element at Index 3 = Delux,
Element at Index 4 = Fan

CustomerIDArray 
Element at Index 0 = 1,
Element at Index 1 = 2,
Element at Index 2 = 2,
Element at Index 3 = 3,
Element at Index 4 = 4

I want result like that Off White = 2 (count) , Fan = 2 (count) and Delux = 1; and the Resultant Array,

Result Array 
Element at Index 0 = Off White,
Element at Index 1 = Fan,
Element at Index 2 = Delux

Actually I want the count of repetition in first array but the value must not same for CustomerArray. Please help me through logic or code.

Answer 1

-(NSMutableArray *)getCountAndRemoveMultiples:(NSMutableArray *)array{

    NSMutableArray *newArray = [[NSMutableArray alloc]initWithArray:(NSArray *)array];
    NSMutableArray *countArray = [NSMutableArray new];
    int countInt = 1;
    for (int i = 0; i < newArray.count; ++i) {
        NSString *string = [newArray objectAtIndex:i];
        for (int j = i+1; j < newArray.count; ++j) {
            if ([string isEqualToString:[newArray objectAtIndex:j]]) {
                [newArray removeObjectAtIndex:j];
                countInt++;
            }
        }
        [countArray addObject:[NSNumber numberWithInt:countInt]];
        countInt = 1;
    }
    NSMutableArray *finalArray = [[NSMutableArray alloc] initWithObjects:newArray, countArray, nil];
    NSLog(@"%@", finalArray);
    return finalArray;

}
- (IBAction)getArrayInfo:(id)sender {
    NSMutableArray *myArray = [[NSMutableArray alloc] initWithObjects:@"Off White", @"Fan", @"Off White", @"Deluxe", @"Fan", nil];
    NSMutableArray *godArray = [self getCountAndRemoveMultiples:myArray];
    NSLog(@"Array from this end = %@", godArray);
}

I just set up -getArrayInfo to test it out. Works fine. As you can see, the array you want to display will be at index:0, and the countArray at index:1.

Answer 2

Use NSCountedSet like below

NSMutableArray *ary_res = [[NSMutableArray alloc] init];
    NSMutableArray *array = [[NSMutableArray alloc] initWithObjects:@"11",@"13",@"34",@"9",@"13",@"34",@"9",@"2",nil];
    NSCountedSet *set = [[NSCountedSet alloc] initWithArray:array];
    for(id name in set)
    {
        if([set countForObject:name]==2)
            [ary_res addObject:name];
    }
    //
    NSLog(@"%@",ary_res);