LeedCode259. Find Median from Data Stream

• For example, for arr = [2,3,4], the median is 3.For example, for arr = [2,3], the median is (2 + 3) / 2 = 2.5.

• MedianFinder.h
  
  #ifndef MEDIANFINDER_H
  #define MEDIANFINDER_H
  
  #include <iostream>
  #include <queue>
  
  using namespace std;
  
  class MedianFinder
  {
      public:
          MedianFinder();
          virtual ~MedianFinder();
          void addNum(int num);
          double findMedian();
          //construct Max heap and Min heap
          priority_queue <int> pq_max;
          priority_queue <int, vector<int>, greater<int>> pq_min;
  
  
      protected:
  
      private:
  };
  
  #endif // MEDIANFINDER_H
  

  MedianFinder.cpp
  
  #include "MedianFinder.h"
  
  MedianFinder::MedianFinder()
  {
      //ctor
  }
  
  MedianFinder::~MedianFinder()
  {
      //dtor
  }
  
  void MedianFinder::addNum(int num)
  {
      //Maintain trees:
      //1.Ensure that the size difference between the two trees is no more than 1;
      //2.Ensure that the top value of Max tree is less than the top value of the Min tree.
      //3.If the Max tree has longer size, compare the top value with num, if num is bigger
      // push num to Min tree, else push Max top value to Mine tree and pop top vale, then push
      // num to Man tree.
      //4. If the Min tree has longer size, compare the top value with num, if num is smaller
      // push num to Max tree, else, push Min top value to Max tree and pop top value, then push
      // num to Mix tree
      if(pq_max.size()==pq_min.size())
      {
          if(pq_max.empty())
          {
              pq_max.push(num);
          }
          else if(num < pq_max.top())
          {
              pq_max.push(num);
          }
          else{
              pq_min.push(num);
          }
      }
  
      else if(pq_max.size()>pq_min.size())
      {
          if(num>pq_max.top())
          {
              pq_min.push(num);
          }
          else
          {
              pq_min.push(pq_max.top());
              pq_max.pop();
              pq_max.push(num);
          }
  
      }
      else if(pq_max.size() < pq_min.size())
      {
          if(num<pq_min.top())
          {
              pq_max.push(num);
          }
          else
          {
              pq_max.push(pq_min.top());
              pq_min.pop();
              pq_min.push(num);
          }
      }
  
  
  }
  double MedianFinder::findMedian(){
  
      //If the size of Max is equal to the size of Min tree, the Median is equal to the
      //average of top values of Min and Max trees.
  
      //Otherwise output the top value of the longer size tree.
      if(pq_max.size()==pq_min.size())
      {
          return (pq_max.top()+pq_min.top())/2.0;
      }
      else if(pq_max.size() > pq_min.size())
      {
          return pq_max.top();
      }
      else
      {
          return pq_min.top();
      }
  
  }

  main.cpp//test
  #include <iostream>
  #include "MedianFinder.h"
  using namespace std;
  
  int main()
  {
      MedianFinder M;
      M.addNum(2);
      M.addNum(1);
      cout<<M.findMedian()<<endl;
      M.addNum(4);
      M.addNum(3);
      cout<<M.findMedian()<<endl;
      return 0;
  }