LeetCode 50. Pow(x, n)

描述
Implement pow(x, n).

分析
二分法，xn = xn/2 × xn/2 × xn%2

代碼

class Solution {
public:
    double myPow(double x, int n) {
        if (n < 0)  return 1.0 / power(x, -n);
        else  return power(x, n);
    }

private:
    double power(double x, int n) {
        if (n == 0) return 1;
        double v = power(x, n / 2);
        if (n % 2 == 0)  return v * v;
        else  return v * v * x;
    }
};