Pow_x_n.cc

class Solution {
public:
    double pow(double x, int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        double ans = 1;
        bool flag = true;
        if (n < 0) {
            flag = false;
            n = -n;
        }
        while (n) {
            if (n % 2 != 0) {
                ans *= x;
            }
            x *= x;
            n /= 2;
        }
        if (flag) {
            return ans;
        }
        return 1.0 / ans;
    }
};