295. Find Median from Data Stream.java

// https://leetcode.com/problems/find-median-from-data-stream/
class MedianFinder {
    PriorityQueue<Integer> minHeap;
    PriorityQueue<Integer> maxHeap;
    public MedianFinder() {
        minHeap = new PriorityQueue<>();
        maxHeap = new PriorityQueue<>(new Comparator<Integer>() {
            public int compare(Integer a, Integer b) {
                return b - a;
            }
        });
    }
    
    public void addNum(int num) {
        minHeap.add(num);
        maxHeap.add(minHeap.poll());
        if (minHeap.size() < maxHeap.size()) {
            minHeap.add(maxHeap.poll());
        }
    }
    
    public double findMedian() {
        if (minHeap.size() > maxHeap.size()) {
            return minHeap.peek();
        } else {
            return (minHeap.peek() + maxHeap.peek()) / 2D;
        }
    }
}

/**
 * Your MedianFinder object will be instantiated and called as such:
 * MedianFinder obj = new MedianFinder();
 * obj.addNum(num);
 * double param_2 = obj.findMedian();
 */