Pow(x, n)

二分法

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