iPhone sdk: how to delete duplicates in the NSArray

问题

Hi My NSArray contains duplicates like this(i have to delete the duplicates)

titles: Father's Day

titles: Election Day

titles: Easter

titles: Earth Day

titles: Cinco de Mayo

titles: Christmas Eve

titles: Christmas titles: Christmas titles: Christmas

I have keep one name only and other duplicates are not wanted. how i have do this please guide me with bit clear explanation, to solve this issue. Thank you.

回答1:

If you care about ordering, you can create a new mutable array, loop through each object in the old array and only add it if it doesn't already exist:

NSMutableArray *uniqueItems = [NSMutableArray array];
for (id item in allItems)
    if (![uniqueItems containsObject:item])
        [uniqueItems addObject:item];

If not, it's much simpler to just use a set:

NSSet *uniqueItems = [NSSet setWithArray:allItems];

回答2:

Is your NSArray that you wish to dedupe already sorted? It appears so from your question. In that case, the following code would do:

NSMutableArray *uniqueItems = [NSMutableArray array];

id lastSeenUniqueObject = nil;

for (NSObject *item in allItems) {
    if (![item isEqual:lastSeenUniqueObject]) {
        [uniqueItems addObject:item];
        lastSeenUniqueObject = item;
    }
}

This has a runtime complexity of N (i.e. fast), as compared to the (approx) N^2 complexity of rpetrich's answer.

If you don't know that the Array's contents is sorted, you have two options:

A) just sort it and then apply the above algorithm, which gives n log n runtime complexity (way better than N^2 still),

B) use an NSMutableSet to track already seen objects (or any other datastructure that uses buckets and hashing). The code would be like this:

NSMutableArray *uniqueItems = [NSMutableArray array];

NSMutableSet *seenItems = [NSMutableSet set];

for (NSObject *item in allItems) {
    if (![seenItems containsObject:item]) {
        [uniqueItems addObject:item];
        [seenItems addOBject:item];
    }
}

This also gives a runtime better than N^2.

回答3:

See simple this..

NSMutableArray *dateArray = [[NSMutableArray alloc]initWithObjects:@"December 29,2010", 
                             @"December 28,2010",
                             @"December 22,2010",
                             @"December 22,2010",
                             @"December 22,2010",@"December 21,2010",@"December 28,2010",nil];

for Avoid Duplicate use this...

NSSet *cleanedArray = [NSSet setWithArray:dateArray];
NSArray *array = [[NSArray alloc]initWithArray:[cleanedArray allObjects]];

for (int i=0; i<[array count]; i++) {
    NSLog(@"The Given Array is %@",[array objectAtIndex:i]);
}

来源：https://stackoverflow.com/questions/5281295/iphone-sdk-how-to-delete-duplicates-in-the-nsarray

标签

iphone

objective-c

nsarray