iOS统计数组相同元素的个数（使用数组筛选计算）

- (void)viewDidLoad {
    [super viewDidLoad];

    //统计数组相同元素的个数

    NSMutableDictionary *dic = [[NSMutableDictionary alloc] init];
    //需要统计的数组
    NSMutableArray *array = [[NSMutableArray alloc]initWithObjects:@"1",@"2",@"2",@"3",@"3",@"3", nil];

    NSSet *set = [NSSet setWithArray:array];
    for (NSString *setstring in set) {
        //需要去掉的元素数组
        NSMutableArray *filteredArray = [[NSMutableArray alloc]initWithObjects:setstring, nil];
        NSMutableArray *dataArray = array;
        NSPredicate * filterPredicate = [NSPredicate predicateWithFormat:@"NOT (SELF IN %@)",filteredArray];

        //过滤数组

        NSArray * reslutFilteredArray = [dataArray filteredArrayUsingPredicate:filterPredicate];
        NSLog(@"Reslut Filtered Array = %@",reslutFilteredArray);
        int number = (int)(dataArray.count-reslutFilteredArray.count);
        NSLog(@"number :%d",number);
        [dic setObject:[NSString stringWithFormat:@"%d",number] forKey:setstring];
    }
    NSLog(@"dic :%@",dic);
    //---------------------------------------------------------------------------------------

//参考数组筛选：

    //需要去掉的元素数组
    NSMutableArray *filteredArray = [[NSMutableArray alloc]initWithObjects:@"1",@"4", nil];
    //需要被筛选的数组
    NSMutableArray *dataArray = [[NSMutableArray alloc]initWithObjects:@"1",@"2",@"1",@"4",@"6",@"1",@"1",@"4",@"1",@"6",@"4", nil];


    /*
     方法一：利用NSPredicate
     注：NSPredicate所属Cocoa框架，在密码、用户名等正则判断中经常用到。
     类似于SQL语句
     NOT 不是
     SELF 代表字符串本身
     IN 范围运算符
     那么NOT (SELF IN %@) 意思就是：不是这里所指定的字符串的值
     */
    NSPredicate * filterPredicate = [NSPredicate predicateWithFormat:@"NOT (SELF IN %@)",filteredArray];

    //过滤数组
    NSArray * reslutFilteredArray = [dataArray filteredArrayUsingPredicate:filterPredicate];
    NSLog(@"Reslut Filtered Array = %@",reslutFilteredArray);
    /*
     结果：
     Reslut Filtered Array = (
     2,
     6,
     6
     )
     */

转载： https://blog.csdn.net/sevenquan/article/details/50593295