字典数组中每个对象的最大值

Question

我有一个字典数组，我试图获取数组中每个玩家的最高分数。每个玩家可以有多个条目我试图获得每个玩家最好成绩的字典数组。

NSArray [0] - NSDictionary

        - [0] Score: (double)20.7
        - [1] NameID: (int) 1
        - [2] Date 

[1] - NSDictionary

        - [0] Score: (double)25
        - [1] NameID: (int) 1
        - [2] Date

[2] - NSDictionary

        - [0] Score: (double)28
        - [1] NameID: (int) 2
        - [2] Date 

[3] - NSDictionary`

        - [0] Score: (double)26
        - [1] NameID: (int) 3
        - [2] Date

我尝试过使用 NSPredicate predicateWithFormat 但我只能取回数组中与名称无关的所有内容的最大值。

预期输出：

NSArray [1] - NSDictionary

        - [0] Score: (double)25
        - [1] NameID: (int) 1
        - [2] Date

[2] - NSDictionary

        - [0] Score: (double)28
        - [1] NameID: (int) 2
        - [2] Date 

[3] - NSDictionary`

        - [0] Score: (double)26
        - [1] NameID: (int) 3
        - [2] Date

感谢您的帮助。

Answer 1

// Get Max Value of integer element from Array of Dictonaries.
// Example Array Starts

<paramArray>(
{
DicID = 1;
Name = "ABC";
ValuetoCalculateMax = 2800;
},
{
DicID = 2;
Name = "DEF";
ValuetoCalculateMax = 2801;
},
{
DicID = 3;
Name = "GHI";
ValuetoCalculateMax = 2805;
}
)
// Example Array Ends

// Implementation


int   MaxintegerValue=0;

MaxintegerValue=[self getMaxValueFromArrayofDictonaries:paramArray];

// Implementation Ends


// Function Starts

-(int)getMaxValueFromArrayofDictonaries:(NSArray *)paramArray
{
int MaxValue=0;
NSMutableDictionary  *dic=[[NSMutableDictionary alloc]init];
for ( int i=0; i<[paramArray count]; i++ )
{
    dic=[paramArray objectAtIndex:i];
    if ([[dic valueForKey:@"ValuetoCalculateMax"] intValue] > MaxValue)
    {
        MaxValue=[[dic valueForKey:@"ValuetoCalculateMax"] intValue];
    }
    else
    {
        MaxValue=MaxValue;
    }
    }
   return MaxValue;
}

// Function Ends

Answer 2

你需要做的是找到每个用户的分数，然后找出它的最高分数。

- (void)findMaxScoreForUser:(int)userId {

NSDictionary *dict0 = [NSDictionary dictionaryWithObjects:@[@27.0,@3] forKeys:@[@"Score",@"UserID"]];
NSDictionary *dict1 = [NSDictionary dictionaryWithObjects:@[@25.0,@2] forKeys:@[@"Score",@"UserID"]];
NSDictionary *dict2 = [NSDictionary dictionaryWithObjects:@[@23.0,@3] forKeys:@[@"Score",@"UserID"]];

NSArray *arr = [NSArray arrayWithObjects:dict0,dict1,dict2, nil];
NSMutableArray *scores = [NSMutableArray array];
for (NSDictionary *dict in arr) {
    int userID = [[dict valueForKey:@"UserID"] intValue];
    if (userId == userID) {
        [scores addObject:[dict valueForKey:@"Score"]];
    }
}

int max = [[scores valueForKeyPath:@"@max.intValue"] intValue];

}

Answer 3

- (NSArray *)getBestScores:(NSArray *)players {
    NSMutableDictionary *best = [[NSMutableDictionary alloc] init];
    for (NSDictionary *p in players) {
        NSDictionary *b = [best valueForKey:[p valueForKey:@"NameID"]];
        if (!b || [[p valueForKey:@"Score"] doubleValue] > [[b valueForKey:@"Score"] doubleValue])
            [best setValue:p forKey:[p valueForKey:@"NameID"]];
    }
    return [best allValues];
}

Answer 4

试试这个：

NSArray *objects = @[@{@"Score": @(20.7),
                       @"NameID": @(1),
                       @"Date": [NSDate date]},
                     @{@"Score": @(25),
                       @"NameID": @(1),
                       @"Date": [NSDate date]},
                     @{@"Score": @(28),
                       @"NameID": @(2),
                       @"Date": [NSDate date]},
                     @{@"Score": @(26),
                       @"NameID": @(3),
                       @"Date": [NSDate date]}];
NSMutableArray *users = [NSMutableArray array];

for (NSInteger i=0; i<objects.count; i++) {

    NSDictionary *dict = objects[i];
    NSNumber *nameID = dict[@"NameID"];

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"self.NameID==%@", nameID];
    NSInteger index = [users indexOfObjectPassingTest:^BOOL(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        BOOL found = [predicate evaluateWithObject:obj];
        return found;
    }];

    if (index != NSNotFound) {
        NSNumber *score1 = dict[@"Score"];
        NSNumber *score2 = users[index][@"Score"];

        if (score1.doubleValue > score2.doubleValue) {
            [users replaceObjectAtIndex:index withObject:dict];
        }
    }
    else {
        [users addObject:dict];
    }
}
NSLog(@"%@", users);

Answer 5

您可以像这样手动操作：

NSMutableDictionary *maxScoresDict = [NSMutableDictionary dictionary];
for (NSDictionary *score in scoresArray) {
    NSNumber *key = score[@"NameID"];
    NSNumber *savedMax = maxScoresDict[key][@"Score"];
    NSNumber *currentMax = maxScoresDict[key][@"Score"];
    if (savedMax == nil || [currentMax doubleValue] > [savedMax doubleValue]) {
        maxScoresDict[key] = score;
    }
}
NSArray *maxScoresArray = [maxScoresDict allValues];

Answer 6

您不能为此使用NSPredicate，因为您想确定几个不同玩家的最高分。在幕后，NSPredicate 无论如何都会迭代数组，因此使用您自己的循环并不会降低效率。在下面的代码中，我假设分数和玩家姓名包含在NSNumber

-(NSArray *)maxScoresForPlayers:(NSArray *)playerScores {

    NSMutableDictionary *maxScores = [NSMutableDictionary new];

    for (NSDictionary *player in playerScores) {
        NSNumber *playerID = (NSNumber *)player[@"NameID"];
        NSDictionary *playerMax = maxScores[playerID];
        if (playerMax == nil) {
           playerMax = player;
        } else {
           NSNumber *currentMax = (NSNumber *)[playerMax[@"Score"];
           NSNumber *playerScore = (NSNumber *)player[@"Score"];
           if ([playerScore doubleValue] > [currentMax doubleValue]) {
                playerMax = player;
           }
        }
        maxScores[playerID] = playerMax;
    }

    return([maxScores allValues];
}