方法一：Insertion Sort

 1 class MedianFinder {
 2     vector<int> store; // resize-able 
 3 public:
 4     /** initialize your data structure here. */
 5     MedianFinder() {
 6         
 7     }
 8     
 9     void addNum(int num) {
10         if (store.empty())
11             store.push_back(num);
12
 
         else
13             // insert(position, value)
14             // lower_bound(interator first, interator last, num) -> return 
15             // return 在range裡第一個小於這個num的位置
16             // binary search combined with insertion
17             store.insert(lower_bound(store.begin(), store.end(), num), num);
 
18     }
19     
20     double findMedian() {
21         int n = store.size();
22         //利用二進位制快速判斷奇偶數
23         return n & 1 ? store[n/2] : ((double) store[n/2 - 1] + store[n/2])*0.5;
24     }
25 };

方法二：Two Heap

 1 class MedianFinder{
 2     //優先佇列建立最大堆
 3     priority_queue<int> lo; // max heap
 
 4     // 優先佇列建立最小堆
 5     priority_queue<int, vector<int>, greater<int>> hi; // min heap
 6 public:
 7     void addNum(int num){
 8         // Add to max heap
 9         lo.push(num);
10         // balance step
11         hi.push(lo.top());
12         
13         lo.pop();
14         
15         // maintain size property
16         if(lo.size() < hi.size()){
17             lo.push(hi.top());
18             hi.pop();
19         }
20     }
21     
22     double findMedian(){
23         return lo.size() > hi.size() ? lo.top() : ((double) lo.top() + hi.top())*0.5;
24     }
25 };