三分模板

const double EPS = 1e-10;

double calc(double n)
{
    return;
}

double solve(double L, double R)
{
    double M, RM;
    while (L + EPS < R)
    {
        M = (L + R) / 2;
        RM = (M + R) / 2;
        if (calc(M) < calc(RM)) //计算最小值
            R = RM;
        else
            L = M;
    }
    return R;
}