powx-n.cpp

// Time:  O(logn)
// Space: O(1)

class Solution {
public:
    double myPow(double x, int n) {
        double res = 1;
        long abs_n = abs(static_cast<long>(n));
        while (abs_n > 0) {
            if (abs_n & 1) {
                res *= x;
            }
            abs_n >>= 1;
            x *= x;
        }
        return n < 0 ?  1 / res : res;
    }
};