LeetCode 0295 - Find Median from Data Stream

Reck Zhang

发布于 2021-08-11 11:47:51

2320

发布于 2021-08-11 11:47:51

文章被收录于专栏：Reck Zhang

Find Median from Data Stream

Desicription

Median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value. So the median is the mean of the two middle value.

For example,

[2,3,4], the median is 3

[2,3], the median is (2 + 3) / 2 = 2.5

Design a data structure that supports the following two operations:

void addNum(int num) - Add a integer number from the data stream to the data structure.
double findMedian() - Return the median of all elements so far.

Example:

addNum(1)
addNum(2)
findMedian() -> 1.5
addNum(3) 
findMedian() -> 2

Solution

class MedianFinder {
private:
    priority_queue<int, vector<int>, greater<>> min_heap;
    priority_queue<int, vector<int>, less<>> max_heap;
public:
    /** initialize your data structure here. */
    MedianFinder() = default;

    void addNum(int num) {
        if(min_heap.size() == max_heap.size()) {
            min_heap.push(num);
            max_heap.push(min_heap.top());
            min_heap.pop();
        } else {
            max_heap.push(num);
            min_heap.push(max_heap.top());
            max_heap.pop();
        }
    }

    double findMedian() {
        return min_heap.size() == max_heap.size() ? (min_heap.top() + max_heap.top()) / 2.0 : max_heap.top();
    }
};

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

本文参与腾讯云自媒体同步曝光计划，分享自作者个人站点/博客。

原始发表：2018-12-21，如有侵权请联系 cloudcommunity@tencent.com 删除

data