滑动窗口的最大值

public class MaxInWindows {

    public List<Integer> maxInWindows(int[] num, int size) {
        List<Integer> ret = new ArrayList<>();
        if (size > num.length || size < 1)
            return ret;
        Queue<Integer> heap = new PriorityQueue<>((o1, o2) -> o2 - o1);  /* 大顶堆 */
        for (int i = 0; i < size; i++)
            heap.add(num[i]);
        ret.add(heap.peek());
        for (int i = 0, j = i + size; j < num.length; i++, j++) {            /* 维护一个大小为 size 的大顶堆 */
            heap.remove(num[i]);
            heap.add(num[j]);
            ret.add(heap.peek());
        }
        return ret;
    }

    public static void main(String[] args) {
        int[] nums = {2, 3, 4, 2, 6, 2, 5, 1};
        List<Integer> windows = new MaxInWindows().maxInWindows(nums, 3);
        System.out.println(windows);
    }
}