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.
Examples:
[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:
For example:
add(1) add(2) findMedian() -> 1.5 add(3) findMedian() -> 2
class MedianFinder { public: // Adds a number into the data structure. void addNum(int num) { maxH.push(num); int t = maxH.top(); maxH.pop(); minH.push(t); int m = maxH.size(), n = minH.size(); if (n > m) { int t = minH.top(); minH.pop(); maxH.push(t); } } // Returns the median of current data stream double findMedian() { int m = maxH.size(), n = minH.size(); if (!m && !n) return 0.0; if (m == n) return (maxH.top() + minH.top()) / 2.0; return (m > n) ? maxH.top() : minH.top(); } private: priority_queue<int, vector<int>, less<int>> maxH; // stores the smaller half priority_queue<int, vector<int>, greater<int>> minH; // stores the larger half }; // Your MedianFinder object will be instantiated and called as such: // MedianFinder mf; // mf.addNum(1); // mf.findMedian();
一个最小堆，一个最大堆，利用了堆的性质。
只需要求中位数。
[LeetCode]Find Median from Data Stream
原文：http://www.cnblogs.com/shenbingyu/p/4908699.html