Median offer prove safety data stream

1. Topic

How to get the median of a data stream? If the numerical value is read from the odd data stream, then the median value is located in the middle of all values ​​after sorting. If an even number value is read out from the data stream, then the median is the average of two numbers after all intermediate values ​​of order. We use the Insert () method to read the data stream, using GetMedian () method to get the current median data is read.

Source: prove safety offer
links: https://www.nowcoder.com/practice/9be0172896bd43948f8a32fb954e1be1?tpId=13&tqId=11216&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking

2. My problem solution

• Top of the heap using large leftsave small half figures, the big top heap righthold larger half figures;
• Determining which of a stack to be inserted is inserted;
• Ensure that the two heap size difference is not more than 1, if not the same size, so big top priority heap left larger;

class Solution {
    priority_queue<int,vector<int>,less<int> > left;//大顶堆
    priority_queue<int,vector<int>,greater<int> >right;//小顶堆
public:
    void Insert(int num)
    {
        if(left.empty() || num<left.top())left.push(num);
        else right.push(num);
        if(left.size()>right.size()+1){
            right.push(left.top());
            left.pop();
        }
        if(right.size()>left.size()){
            left.push(right.top());
            right.pop();
        }
    }

    double GetMedian()
    { 
        if(left.empty() && right.empty())return 0;
        if(left.size()==right.size()+1)return left.top();
        return 0.5 * (left.top()+right.top());
    }

};

3. someone else's problem solution

4. Summary and Reflection

(1) C++in
priority_queue<int,vector< int >,less< int > >the default heap big top;

priority_queue<int,vector< int >,greater< int > >small pile top;