top K 问题 大顶堆AC了，没什么难度

        ArrayList<Integer> res = new ArrayList<>();
        if (input.length == 0) return res;
        input = createBigHeap(input);
        for (int i = 0; i < k; i++) {
            res.add(input[i]);
        }
        return res;
    }
    public int[] createBigHeap(int[] nums) {
        //初始化并创建堆，主要想在索引0下找到数组最大值
        int length = nums.length;
        for (int i = (length - 1) / 2; i >= 0; i--) {
            adjustBigHeap(nums, i, length);
        }
        for (int i = length - 1; i >= 0; i--) {
            swap(nums, 0, i);
            adjustBigHeap(nums, 0, i);
        }
        return nums;
    }
    //这里我递归调整了一下
    public void adjustBigHeap(int[] nums, int parent, int length) {
        int pivt = nums[parent];
        int lChild = 2 * parent + 1;
        if (lChild < length) {
            int rChild = lChild + 1;
            int max = lChild;
            if (rChild < length && nums[rChild] > nums[lChild]) max = rChild;
            if (pivt >= nums[max]) return;
            swap(nums, parent, max);
            adjustBigHeap(nums, max, length);
        }
    }
    public void swap(int[] nums, int i, int j) {
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }