double pow (double base     , double exponent);

      float pow (float base      , float exponent);

long double pow (long double base, long double exponent);

     double pow (Type1 base      , Type2 exponent);        // additional overloads

int mypow(int x, int y)

{

    if (y == 1) return x;

    int result = 0;

    int tmp = mypow(x, y/2);

    if(y&1 != 0) //奇数

    {

        result = x * tmp * tmp;

    }

    else

    {

        result = tmp * tmp;

    }    

    return result;

}