2 задача. функция set()

void set(const int old_id,const int new_element,const int x,const int lx,const int rx, vector<int>& array)
{
    if (rx - lx == 1)
    {
        array[x] = new_element;
        return;
    }
    int m = (rx+lx) / 2;
    if (old_id < m)
    {
        set(old_id, new_element, 2 * x + 1, lx, m,  array);
    }
    else
    {
        set(old_id, new_element, 2 * x + 2, m, rx, array);
    }
    array[x] = array[2 * x + 2] + array[2 * x + 1];
}