剑指offer--47.数据流中的中位数

class Solution {
    public:
        void Insert(int num) {
            arr.push_back(num);
        }

        double GetMedian() {
            sort(arr.begin(), arr.end());
            int len = arr.size();
            if(len == 0) return 0;
            if(len == 1) return arr[0];
            if(len == 2) return (arr[0] + arr[1])*1.0/2;
            if(len & 1) {
                return arr[len/2]*1.0;
            } else {
                return (arr[len/2] + arr[len/2-1])*1.0 /2;
            }
        }
    private:
        vector<int> arr;
};