在Java中实现Comparable的堆

Question

I have an array that is full of Doubles and I want to save those doubles in a heap. The problem is I need to keep record of the index of the array.

Double[] array = new Double[n]; //imagine it's filled with doubles

Now I have a PriorityQueue:

PriorityQueue<Integer> heap = new PriorityQueue<Integer>(); //Integer because it's an heap of indexes

I want to add each element of the array to the heap, but I want to keep record of the INDEX. So imagine I add index 0 to the heap:

The heap stores 0, but uses array[0] to compare and sort it.
Not index 0 itself, that's just like a class index. Stores v but compares v.value

When I get a value from the heap:

Imagine I do heap.pull();
The heap returns me index 0, and then I will know the value is array[0].

Can I do this with comparable?

Answer 1

I hope I understand your question well. Try running the example below. See if you understand it and if this is the behaviour you are looking for.

int n = 10;
final double[] arr = new double[n];
for (int i = 0; i < n; ++i) {
    arr[i] = Math.random() * 100;
}
PriorityQueue<Integer> queue = new PriorityQueue<>(n, new Comparator<Integer>() {
    @Override
    public int compare(Integer o1, Integer o2) {
        return (int) (arr[o1] - arr[o2]);
    }
});

for (int i = 0; i < n; ++i) {
    queue.add(i);
}

System.out.println(Arrays.toString(arr));
System.out.println(queue.toString());

Note this can result in an OutOfBoundsException very quickly when you add something unexpected to the PriorityQueue .