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How do I remove duplicates in NSMutableArray

I am not sure how to remove duplicate numbers in a NSMutableArray and whether to remove them before sorting or not. And is there an easy way to remove duplicate numbers before they are even added to the array? This is not homework.

#import <Foundation/Foundation.h>
 
int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc]init];
    
    NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc]init];
    [numberFormatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
    [numberFormatter setFormat:@"00"];
    NSString *myNumberString;
    NSMutableArray *array;
    int i;
    NSNumber *newNumber;
    NSNumber *numbersToPrint;
 
    printf ("\n");
    array = [[NSMutableArray alloc]init];
    // Initialize the random number generator.
    srandom(time(NULL));
    for (i = 0; i < 6; i++) {
        newNumber = [[NSNumber alloc]initWithInt:random() % 55 + 1];
        myNumberString = [numberFormatter stringFromNumber:newNumber];
        [array addObject:myNumberString];
        [array sortUsingSelector:@selector(compare:)];
        [newNumber release];
    }
 
    // Using NSLog
    for (i = 0; i < 6; i++) {
        numbersToPrint = [array objectAtIndex:i];
        NSLog(@"The number at index %d is %@.", i, numbersToPrint);
    }
 
    [array release];
    [pool drain];
 
    return 0;
}

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AJVienna

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romanm

Use insertion sort, find the location to insert using a binary search,

insertion loop would look like this:

start = 0
end = array count
if array empty
add item, go to next item.
1. search position = start + ((end - start) / 2), round down
2. if insert item equals item at search position, exit search and go to next item to insert
3. else if insert item is greater than the item at search position,
if search position equals end
insert at end
else
start = search position + 1
4. else
if search position equals start
insert before start
else
end = search position
5. if start equals end
insert item after start.
6. else
go to 1

so you get the insertion of a NSMutableSet, unique values and sorted, and save the need to copy.

AJVienna

@romanm, the binary search is only useful if there are more elements. With only 6 random numbers it will cause more overhead than benefit.

romanm

how will it cause more overhead then using a set?
a set uses a binary search too, a set has a red-black tree balancing each time you insert, (I am talking windows but I think same applies).

proposed algorithm is a shortcut over using a set, count of elements is irrelevent.