How to count duplicates values in NSArray?

Question

Value of my NSArray includes the duplicates. I find the duplicates but now how can I find the no. they repeat?

How are you finding the duplicates? If you're stepping through the array values and comparing them, you should be able to incriment an int whenever you hit a duplicate value. — Aurum Aquila
– Aurum Aquila, Commented Jul 27, 2011 at 7:53
NSArray *cleanedArray = [[NSSet setWithArray:duplicateElements] allObjects]; By this code I remove duplicates. — iDev
– iDev, Commented Jul 27, 2011 at 9:24
Yeah, I don't think you're going to be able to get a count out of that method. Look at @omz suggestion, it seems like it's going to work a treat. Then you can call the [[NSSet setWithArray:duplicateElements] allObjects]; methods. — Aurum Aquila
– Aurum Aquila, Commented Jul 27, 2011 at 11:09

omz · Accepted Answer · 2011-07-27 07:53:58Z

37

You can use NSCountedSet for this. Add all your objects to a counted set, then use the countForObject: method to find out how often each object appears.

answered Jul 27, 2011 at 7:53

omz

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Aurum Aquila Over a year ago

Actually, I'll just +1 this answer and bookmark it in Chrome.

Jakub Truhlář · Accepted Answer · 2015-01-06 19:11:31Z

9

Example:

NSArray *names = [NSArray arrayWithObjects:@"John", @"Jane", @"John", nil];
NSCountedSet *set = [[NSCountedSet alloc] initWithArray:names];

for (id item in set) {

    NSLog(@"Name=%@, Count=%lu", item, (unsigned long)[set countForObject:item]);
}

answered Jan 6, 2015 at 19:11

Jakub Truhlář

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Comments

Mihai Fratu · Accepted Answer · 2011-07-27 07:58:22Z

1

You can try something like this

__block NSInteger elementCount = 0;
NSArray *array;

[<#NSArray yourArray#> indexesOfObjectsPassingTest:^(id obj, NSUInteger idx, BOOL *stop){
    if (obj == <#yourObject#>) {
        elementCount++;
        return YES;
    }
    return NO;
}];

Let me know if that works for you

answered Jul 27, 2011 at 7:58

Mihai Fratu

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