lintcode: Data Stream Median

Numbers keep coming, return the median of numbers at every time a new number added.

维持一个大顶堆，一个小顶堆；大顶堆存有序的前一半数据，小顶堆存有序的后一半数据；大顶堆的堆顶就是每次的中位数。

注意要 维持maxHeap.size()==minHeap.size()+1或者maxHeap.size()==minHeap.size()

参考：​​javascript:void(0)​​

class Solution {
public:
    /**
     * @param nums: A list of integers.
     * @return: The median of numbers
     */
    struct mycmp{
       bool operator()(const int a,const int b)const{
           return a>b;
       } 
    };

    vector<int> medianII(vector<int> &nums) {
        // write your code here

        vector<int> res;
        int len=nums.size();
        if(len==0){
            return res;
        }

        priority_queue<int> maxHeap;
        priority_queue<int,vector<int>,mycmp> minHeap;

        maxHeap.push(nums[0]);
        res.push_back(nums[0]);

        for(int i=1;i<len;i++){
            if(nums[i]<=maxHeap.top()){
                maxHeap.push(nums[i]);
            }else{
                minHeap.push(nums[i]);
            }

            /*维持maxHeap.size()==minHeap.size()+1或者maxHeap.size()==minHeap.size()*/

            if(maxHeap.size()>minHeap.size()+1){
                int top=maxHeap.top();
                maxHeap.pop();
                minHeap.push(top);
            }

            if(maxHeap.size()<minHeap.size()){
                int top=minHeap.top();
                minHeap.pop();
                maxHeap.push(top);
            }

            res.push_back(maxHeap.top());
        }

        return res;
    }
};