几个算法

+ (NSString *)chinaNumberWithIndex:(NSUInteger)index{
    if (index == 0) { //特殊处理
        return @"零";
    }
    NSString *str = [NSString stringWithFormat:@"%ld",index];
    NSString *result = @"";
    NSInteger lastmm = 0;
    NSArray *array = @[@"零",@"一",@"二",@"三",@"四",@"五",@"六",@"七",@"八",@"九"];
    NSArray *arr   = @[@"个",@"十",@"百",@"千",@"万"];
    for (int i = 0; i < str.length; i ++) {
        NSInteger mm = index % 10;
        index /= 10;
        if (i == 0) {
            if (mm != 0) {
                result = [array objectAtIndex:mm];
            }
            lastmm = mm;
        }else{
            if (str.length == 2 && i == 1 && mm == 1) { //11  读作 十一而非一十一 ，特殊处理
                result = [NSString stringWithFormat:@"十%@",result];
            }else
            if (mm == 0) {
                if (mm != lastmm) {
                    result = [NSString stringWithFormat:@"零%@",result];
                }
            }else{
                result = [NSString stringWithFormat:@"%@%@%@",[array objectAtIndex:mm],[arr objectAtIndex:i],result];
            }
            lastmm = mm;
        }
    }
    return result;
}

    int index = arc4random_uniform(100000);
    NSLog(@"%d:%@",index,[ViewController chinaNumberWithIndex:index]);

14833:一万四千八百三十三

-(NSIndexSet *)getRandomWithIndex:(NSInteger)number count:(NSInteger)count{
    if (number > count) {
        return nil;
    }
    NSMutableArray *array = [NSMutableArray array];
    for (int i = 0; i < count; i ++) {
        [array addObject:[NSString stringWithFormat:@"%d",i]];
    }
    NSMutableIndexSet *indexSet2 = [NSMutableIndexSet indexSet];
    for (int i = 0 ; i < number; i ++) {
        int index = arc4random_uniform((int)array.count);
        NSString *str = [array objectAtIndex:index];
        [indexSet2 addIndex:[str integerValue]];
        [array removeObject:str];
    }
    return [[NSIndexSet alloc]initWithIndexSet:indexSet2];
}

 NSLog(@"%@",[self getRandomWithIndex:9 count:89]);

<NSIndexSet: 0x7fdc48cbb5f0>[number of indexes: 9 (in 8 ranges), indexes: (9 16 30 38 69 76-77 84 88)]