leetcode - Pow(x, n)

class Solution {public:    double pow(double x, int n) {double res = 1;if(x == 1)return 1;if(x == -1){if(n % 2) return -1;else return 1;}bool flag = false;if(n < 0){n = -n;flag = true;}while(n)  //快速幂{if(n & 1)res *= x;x *= x;n >>= 1;}if(flag) res = 1 / res;#if 1std::cout << res << std::endl;#endif // 1return res;    }};