Pow(x, n)

Implement pow(x, n).

class Solution {
public:
double pow(double x, long long n) {
if(n==0)
return 1.0;
if(n<0)
return 1.0/pow(x,-n);
double half=pow(x,n/2);
if(n%2==0)
return half*half;
else
return half*half*x;
}
double myPow(double x, int n) {
return pow(x, n);
}
};