二分查找模板

/*
最左边n结束，>> 位移运算，low = mid + 1，high = mid;
*/
 int upper_bound_(int n, int v, vector<int>& a) {
        int low = 0,high = n;
        while(low<high){
            int mid =low+high >> 1;//位移运算优先级低于+-*/
            a[mid]<v?low=mid+1:high=mid; //最先找到满足大于等于v的最小下标值
        }
        return low+1;
    }