啊哈哈哈，挺简单的
数据流中的中位数
http://www.nowcoder.com/questionTerminal/9be0172896bd43948f8a32fb954e1be1
class Solution {
public:
vectora;
void Insert(int num)
{
a.insert(a.begin(),num);
}
double GetMedian()
{
sort (a.begin(),a.end());
if(a.size()%2==1)
return (double)*(a.begin()+(a.size()-1)/2);
else if(a.size()%2==0)
return (double)(*(a.begin()+a.size()/2)+*(a.begin()+a.size()/2-1))/2;
}};
