Java - 获取一个int数组的升序索引

Question

我有一个 int 数组 [2,4,1,0,0,3] 并且需要从中获取一个按升序排列的索引数组，意思是 [3,4,2,0,5,1 ].

我尝试通过使用排序数组按顺序获取数字来解决此问题，然后迭代原始数组以在匹配发生时查找索引。如下:

public class IndexAscendingSorter {
    public static void main (String[] args) {
        int[] array = {2,4,1,0,0,3};
        IndexAscendingSorter finder = new IndexAscendingSorter();
        int[] indixes = finder.orderIndexAscending(array);

        System.out.println("Indexes of the array in ascending order: " +
                            Arrays.toString(indixes));
    }

    public int[] orderIndexAscending(int[] array) {
        int[] minimumIndexes = new int[array.length];
        int[] sortedArray = array.clone();
        Arrays.sort(sortedArray);

        for (int index = 0; index < array.length; index++){
            int minIndex = 0;
            for (int number : array) {
                if (number == sortedArray[index]) { 
                    minimumIndexes[index] = minIndex;
                    break;
                }
                minIndex++;
            }
        }
        return minimumIndexes;
    }
}

问题是对于相同的数字不返回正确的索引，执行该代码的输出是:

Indexes of the array in ascending order: [3, 3, 2, 0, 5, 1] The second value array[1] should have been 4 instead of 3. Does anyone know how can I improve this?

Answer 1

继续您的方法，一个快速的解决方案是使用哈希集，您将在其中添加您已经使用的索引，然后可以检查它是否是重复索引。只需将 orderIndexAscending() 函数更改为:

    public int[] orderIndexAscending(int[] array) {
        int[] minimumIndexes = new int[array.length];
        int[] sortedArray = array.clone();
        Arrays.sort(sortedArray);
        Set<Integer> savedIndexes = new HashSet<>();

        for (int index = 0; index < array.length; index++){
            int minIndex = 0;
            // Add the index in ascending order, we need to keep the indexes already
            // saved, so won't miss indexes from repeted values
            for (int number : array) {
                if (number == sortedArray[index] && !savedIndexes.contains(minIndex)) { 
                    savedIndexes.add(minIndex);
                    minimumIndexes[index] = minIndex;
                    break;
                }
                minIndex++;
            }
        }
        return minimumIndexes;
    }
}