295. Find Median from Data Stream

2-stack solution

Code

 class MedianFinder {
    priority_queue<int, vector<int>, greater<int>> min_heap;
    priority_queue<int> max_heap;

public:
    MedianFinder() { }

    void addNum(int num)
    {
        if (max_heap.empty() || num < max_heap.top()) {
            max_heap.push(num);
        } else {
            min_heap.push(num);
        }

        if (max_heap.size() > min_heap.size() + 1) {
            min_heap.push(max_heap.top());
            max_heap.pop();
        } else if (max_heap.size() + 1 < min_heap.size()) {
            max_heap.push(min_heap.top());
            min_heap.pop();
        }
    }

    double findMedian()
    {
        if (max_heap.size() == min_heap.size()) {
            return max_heap.empty() ? 0 : (max_heap.top() + min_heap.top()) / 2.0;
        } else {
            return (max_heap.size() > min_heap.size()) ? max_heap.top() : min_heap.top();
        }
    }
};