powCpp

class Solution {
public:
    double myPow(double x, int n) {
        double ans = 1.0; 
        long long nn = n; 
        if(nn<0) nn = -1 * nn;
        while(nn) {
            if(nn % 2) {
                ans = ans * x; 
                nn = nn - 1; 
            }
            else {
                x = x * x; 
                nn = nn / 2; 
            }
        }
        if(n<0) ans = (double)(1.0) / (double)(ans); 
        return ans; 
    }
};