double positivePow(double x, unsigned n) {
if (0 == n) {
return 1;
}
double result = positivePow(x, n / 2);
result *= result;
return (n % 2 == 0) ? result : result * x;
}
double myPow(double x, int n) {
if (n == 0) return 1;
else if (n < 0) return 1 / positivePow(x, -n);
else return positivePow(x, n);
}
double myPow(double x, int n) {
return n > 0 ? positivePow(x, n) : 1 / positivePow(x, -n);
}