C++二分查找

int search(vector<int>vec,int num)
{

    int left=0;
    int right=vec.size()-1;

    while(left<=right)
    {
        int mid=(left+right)/2;

        if(vec[mid]>num)
        {
            right=mid-1;
        }
        else if(vec[mid]<num)
        {

            left=mid+1;
        }
        else {
            return mid;
        }
    }return -1;
}