NSSet 集合

最有用的功能：去重，排序

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];
   
//    利用set不会重复添加元素的特性去重

    NSArray *array = @[@22,@44,@123,@33,@33,@22,@44];

    NSSet *set = [NSSet setWithArray: array];

    NSLog(@"%@",[set allObjects]);
    
    NSArray *array1 = @[@22,@44,@123,@33,@33,@22,@44];

//去重，利用字典Dictionary本身不能有key，value重复的特性去重。

    NSMutableDictionary *dict = [NSMutableDictionary dictionary];

   [array enumerateObjectsUsingBlock:^(id  _Nonnull key, NSUInteger idx, BOOL *_Nonnull stop) {
        dict[key] =@1;
    }];

    array1 = [dict allKeys];
    NSLog(@"%@", array1);
    
    //可以用index 索引
    NSOrderedSet *orderSet = [NSOrderedSet orderedSet];
    
}

@end

冒泡排序

    NSMutableArray *array3 = @[@22,@44,@123,@33,@33,@22,@44];
    
    for (int i = 0; i < array3.count; i++) {
        for (int j = 0; j < array3.count - 1 - i; j++) {
            if (array3[j] > array3[j + 1]) {
                [array3 exchangeObjectAtIndex:j withObjectAtIndex:j + 1];
            }
        }
    }
    
  [array3 sortUsingComparator:^NSComparisonResult(id  _Nonnull obj1, id  _Nonnullobj2) {
        if (obj1 > obj2) {
            //降序
            return NSOrderedDescending;
        }else if(obj1 < obj2){
            //升序
            return NSOrderedAscending;
        }
        else {
            return NSOrderedSame;
        }
    }];

    NSLog(@"--->%@", array3);