Java优先队列

static Comparator<Integer> cmp = new Comparator<Integer>(){
    public int compare(Integer e1,Integer e2){
        return e1 - e2;//默认升序排列，大根堆
    }
};
Queue<Integer> q = new PriorityQueue(cmp);

剑指 Offer 40. 最小的k个数

    static Comparator<Integer> cmp = new     Comparator<Integer>(){
        public int compare(Integer e1,Integer e2){
            return e2 - e1;
        }
    };
    public int[] getLeastNumbers(int[] arr, int k) {
        if(arr.length ==0 || k == 0) return new int[0];
        int []res = new int[k];
        Queue<Integer> q = new PriorityQueue(cmp);
        for(int i = 0;i < k;i++){
            q.offer(arr[i]);
        }
        for(int i = k;i < arr.length;i++){
            if(arr[i] < q.peek()){
                q.poll();
                q.offer(arr[i]);
            }
        }
        int idx = 0;
        while(!q.isEmpty()) res[idx++] = q.poll();
        return res;
    }
``