Changing Java PriorityQueue to a Max PQ

user_395082 0
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The Priority Queue implementation in the Java standard library appears to be a min Priority Queue which I found somewhat confusing. In order to turn it into a max one I created a custom comparator object.

Comparator<Integer> cmp = new Comparator<Integer>()
{
    public int compare( Integer x, Integer y )
    {
        return y - x;
    }
};

I was wondering if there was a more elegant solution. Essentially I wan't a generic priority queue that could be used to implement Dijkstras etc. I didn't even realise there would be ones which operated in reverse :/

standard-library priority-queue java
4 Answers

Not sure what you mean by elegant but when I want a PQ implemented like a MaxHeap (used in Dijkstra's) I just use an inline comparator constructor.

PriorityQueue<Integer> PQ= new PriorityQueue<Integer>(20, new Comparator<Integer>(){
            public int compare(Integer o1, Integer o2){
                return o2 - o1;
            }
        });

It's simple enough for anytime I'm looking for something simple and only want to use the Comparator once.

user_13072470
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