ios - 获取 3 个有序值的数组，同时支持指定值

Question

抱歉，标题有点笼统，如果有人有更好的建议请告诉我。

基本上我正在编写一个自定义排行榜 View ，我只想显示 3 个分数。如果可能，它会在中间显示当前用户的分数，但如果用户位于列表的顶部或底部，它仍应显示 3 个分数，但会在列表上方或下方显示其他用户。

例如

1. 我(如果我在最前面，则在下面显示 2)
2. 用户 1
3. 用户 2

或

1. 用户 1
2. 我(通常情况下我在两个分数中间)
3. 用户 2

或

1. 用户 1
2. 用户 2
3. 我(如果我垫底，显示比我高两分)

我编写了一个函数来完成第一部分，但没有考虑到我正在努力解决的边缘情况。任何人都可以请教吗？

-(void)getNearbyScores:(int)score{
    GCLeaderboardScore *closestScoreAbove = nil; //Custom container for GC properties
    GCLeaderboardScore *closestScoreBelow = nil; //Contains playerID, score, alias etc

    if ([playerScores count] == 0){ //playerScores is an NSMutableDictionary
        return;
    }

    for (NSString* key in playerScores) {

        GCLeaderboardScore *playerScore = (GCLeaderboardScore *)[playerScores objectForKey:key];
        if ((closestScoreAbove == nil || closestScoreAbove->score > playerScore->score)  && playerScore->score > score){
            closestScoreAbove = playerScore;
        }
        else if ((closestScoreBelow == nil || closestScoreAbove->score < playerScore->score) && playerScore->score < score){
            closestScoreBelow = playerScore;
        }
    }

    me->score = score;
    me->rank = 1;
    if (closestScoreAbove != nil) {
        me->rank = closestScoreAbove->rank + 1;
        nearbyScores = [NSMutableArray arrayWithObjects: closestScoreAbove, me, closestScoreBelow, nil];
    }
    else {
        nearbyScores = [NSMutableArray arrayWithObjects: me, closestScoreBelow, nil];
    }
}

Answer 1

假设有一个 me GCLeaderboardScore 对象，下面的方法应该返回一个包含所需 GCLeaderboardScore 对象的数组(未经测试):

-(NSArray *)getNearbyScores {

    if(playerScores.count==0) return nil;

    // Create an array sorted by score
    NSArray *sortedByScore=[playerScores sortedArrayUsingComparator: ^(id object1, id object2) {
        GCLeaderboardScore  *score1=object1;
        GCLeaderboardScore  *score2=object2;

        if(score1->score < score2->score) return NSOrderedAscending;
        if(score1->score > score2->score) return NSOrderedDescending;

        return NSOrderedSame;
    }];

    // Find index of me
    NSUInteger  idx=[sortedByScore indexOfObject:me];

    // If me not found, return nil
    if(idx==NSNotFound) return nil;

    // Ideally we want to show the player before and behind
    idx=MAX(0,(NSInteger)idx-1);

    // maxIdx will be idx+2 or index of last object if lower
    NSUInteger  maxIdx=MIN(sortedByScore.count-1,idx+2);

    // In case we are last, show two previous results (if array large enough)
    if (maxIdx > 3)
                idx=MAX(0,maxIdx-3);

    // And return the objects, may be 1..3 objects
    return [sortedByScore subarrayWithRange:NSMakeRange(idx,maxIdx-idx+1)];
}