获得一个无序的双数组索引排序后 [英] Getting the indices of an unsorted double array after sorting

问题描述

这个问题来为这个伴侣<一个href=\"http://stackoverflow.com/questions/25802052/getting-the-largest-k-elements-of-a-double-array\">one这算是最快的排序双阵列。

This question comes as a companion of this one that regarded fastest sorting of a double array.

现在我想要得到的顶部 - K对应的排序的数组指数

Now I want to get the top-k indices corresponding to the unsorted array.

我已经实现了这个版本，它（不幸）使用自动装箱和的HashMap 在一些答案，包括这个的 之一：

I have implemented this version which (unfortunately) uses autoboxing and HashMap as proposed in some answers including this one:

HashMap<Double, Integer> map = new HashMap<Double, Integer>();
for(int i = 0; i < numClusters; i++) {
    map.put(scores[i], i);
}
Arrays.sort(scores);
HashSet<Integer> topPossibleClusters = new HashSet<Integer>();
for(int i = 0; i < numClusters; i++) {
    topPossibleClusters.add(map.get(scores[numClusters - (i+1)]));
}

正如你可以看到这个使用了的HashMap 的钥匙原始数组，并作为双击值的值的原数组的索引。
因此，整理原始数组后，我刚刚从<$ ​​C $ C>地图检索。

As you can see this uses a HashMap with keys the Double values of the original array and as values the indices of the original array. So, after sorting the original array I just retrieve it from the map.

我也用 HashSet的，因为我很感兴趣，决定是否在 INT 包含在这一套，使用。载有（）方法。 （我不知道这使得因为我在其他问题中提到的差异我的数组是小-50元素 - ）。如果这不会有所作为点出来，虽然。

I also use HashSet as I am interested in deciding if an int is included in this set, using .contains() method. (I don't know if this makes a difference since as I mentioned in the other question my arrays are small -50 elements-). If this does not make a difference point it out though.

我不感兴趣的价值本身，只有指数。

I am not interested in the value per se, only the indices.

我的问题是，是否有一个更快的方法去用它？

My question is whether there is a faster approach to go with it?

推荐答案

这有点互连的/联锁集合适合于脆弱，易断，难以调试，难以维护code。

This sort of interlinking/interlocking collections lends itself to fragile, easily broken, hard to debug, unmaintainable code.

而不是创建一个对象：

class Data {
    double value;
    int originalIndex;
}

创建数据对象存储原始值和索引数组

Create an array of Data objects storing the original value and index.

使用自定义的比较，着眼于data.value和排序降序排序它们。

Sort them using a custom comparator that looks at data.value and sorts descending.

现在您的数组中的顶的X项目是你想要的，你可以只是看看值和 originalIndex ，你需要他们。

Now the top X items in your array are the ones you want and you can just look at the value and originalIndex as you need them.

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