LeetCode 703. Kth Largest Element in a Stream

[Woodyiiiiiii]

1. 用最小堆；
2. 每次add元素进最小堆中，并不会比较堆顶，而是会重新排序
3. 堆问题解决TOP K问题
4. 此题是一道变种题，每次堆大小超过堆就抛出，起到比较和筛选的作用，取数也只跟堆顶有关，跟堆内元素无关

class KthLargest {
    
    PriorityQueue<Integer> queue;

    int k = 0;

    public KthLargest(int k, int[] nums) {

        this.k = k;

        queue = new PriorityQueue<>(k);

        for (int num : nums) {
            queue.add(num);
            if (queue.size() > k) {
                queue.poll();
            }
        }

    }

    public int add(int val) {

        queue.add(val);

        if (queue.size() > k) {
            queue.poll();
        }

        return queue.peek();

    }
}

/**
 * Your KthLargest object will be instantiated and called as such:
 * KthLargest obj = new KthLargest(k, nums);
 * int param_1 = obj.add(val);
 */