数字在排序数组中出现的次数

class Solution {
public:
    int GetNumberOfK(vector<int> data ,int k) {
        if(data.empty())
            return 0;
        return GetNumberOfKCore(data,k+0.5)-GetNumberOfKCore(data,k-0.5);
    }
private:
    int GetNumberOfKCore(vector<int> data,double k)
    {
        int left=0,right=data.size()-1;
        while(left<=right)
        {
            int mid=(right-left)/2+left;
            if(data[mid]<k)
                left=mid+1;
            else if(data[mid]>k)
                right=mid-1;
        }
        return left;//also right
    }
};