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up vote 3 down vote favorite
1

I want to compare 2 NSMutableArray and get different object into third Array. How can i do that ?

Array1 can loop object .

Array1 = "a", "b","c","d","a","b","c";
Array2 = "a", "b", "c";

And then result 

Array3 = "d";

Thanks in advance

share|improve this question
    
Should array3 just be [ "d" ], or should it be [ "b", "d" ], your question isn't clear about what 'diff object' means? –  Wain Jul 12 '13 at 9:26
    
Are the objects strings? Also, are you looking for equality (the value is the same) or identity (which objects in array1 occupy the same memory as the objects in array2)? –  Maarten Jul 12 '13 at 9:26
    
@Wain: i edited my question –  NGOT Jul 12 '13 at 9:28
    
@Maarten: Yes, it is a object –  NGOT Jul 12 '13 at 9:28
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4 Answers

up vote 12 down vote

Use sets for set operations:

NSSet *set1 = [NSSet setWithArray:array1];
NSMutableSet *set2 = [NSMutableSet setWithArray:array2];
[set2 minusSet:set1];
share|improve this answer
1  
+1 @NGOT using NSSet is efficient. –  βhargavḯ Jul 12 '13 at 9:45
    
I trying above code but in console set2 always = 0 –  NGOT Jul 12 '13 at 9:48
    
@NGOT, are you using really string literals as in the question, or some objects of a custom class? –  vikingosegundo Jul 12 '13 at 9:49
1  
@NGOT: You have to swap array1 and array2 because in this answer, array2 is the "larger" array. –  Martin R Jul 12 '13 at 9:52
    
@MartinR Oh, sorry for expecting people to know highschool maths. I apologize. </sarcasm> - and thanks for explaining that to OP. –  user529758 Jul 12 '13 at 9:53
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up vote 4 down vote

You Can try this too.

NSMutableArray *array1 = [[NSMutableArray alloc]initWithObjects:@"1",@"2",@"3",@"1", nil];
NSMutableArray *array2 = [[NSMutableArray alloc]initWithObjects:@"2",@"1", nil];    

NSMutableArray *largeArray;
NSMutableArray *shortArray;
if([array1 count] > [array2 count]){
    largeArray = array1;
    shortArray = array2; 
} else {
    largeArray = array2;
    shortArray = array1; 
}
[largeArray removeObjectsInArray:shortArray];

for (NSString *va in largeArray) {
    NSLog(@"%@",va);
}
share|improve this answer
    
HOw can determine that which one is large and which one is short ? –  Ranju Patel Jul 12 '13 at 9:38
    
@RanjuPatel like you have array in which you want to check the duplicates (the duplicates are also in the array). –  Bunty M Jul 12 '13 at 9:45
    
really nice and smart answer bro :) –  Ranju Patel Jul 12 '13 at 10:08
    
@vikingosegundo & ranju thanks good luck. –  Bunty M Jul 12 '13 at 10:17
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up vote 4 down vote

I have used the following and got the desired results:

for(int i =0; i<[arraytwo count]; i++)
{
    if (![arrayone containsObject:[arraytwo objectAtIndex:i]])
        [arraythree addObject: [arraytwo obectAtIndex:i]];
}    
NSLog(@"%@",arraythree);
share|improve this answer
    
Probably more efficient than the set approach (for smaller arrays, at least). –  Hot Licks Jul 12 '13 at 11:52
    
I am using it for bigger arrays too. It may take some time for bigger array, but i am doing it in background so works fine. –  Ankit Mehta Jul 12 '13 at 13:05
    
Yeah, it's just that I haven't gone through a "big O" estimation for the various schemes. Probably the set approach is a hair more efficient for large sets, but you likely have to be in the thousands of elements for it to be significant. –  Hot Licks Jul 12 '13 at 14:55
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up vote 2 down vote 
NSMutableArray *gotDiffArry= [[NSMutableArray alloc] init];
for(int i = 0 ; i < FirstArray.count; i++) {
    if(i < seconArray.count){
        if(![seconArray[i] isEqual:firstArray[i]]){
             [gotDiffArry addObject:[NSNumber numberWithInt:i]];
         }
    } else {
        [gotDiffArry addObject:[NSNumber numberWithInt:i]];
    }
}

EDITED:

for (int i = 0 ; i < firstArray.count ; i ++)
{

 NSString *search = [firstArray objectAtIndex:i];
 NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY SELF CONTAINS %@", search];
 NSMutableArray *temAraay = [secondArray filteredArrayUsingPredicate: predicate];
 if(temArray.count >=0 )
 {
   NSLog("%@", [temArray objectAtIndex:0]); 
 }
}
share|improve this answer
    
what type of differentIndex? –  NGOT Jul 12 '13 at 9:37
    
This is too iterative and time consuming if arrays are large. Not an efficient way. –  βhargavḯ Jul 12 '13 at 9:42
    
Thanks but i only want to get diff object not all object. –  NGOT Jul 12 '13 at 9:46
    
@NGOT- then use only else part of Array ...:) –  Ranju Patel Jul 12 '13 at 9:47
    
@NGOT-check my edited answer :) –  Ranju Patel Jul 12 '13 at 10:07
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