LeetCode: Pow(x, n)

class Solution {
public:
    double pow(double x, int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (n == 0) return 1;
        if (x == 0) return 0;
        bool flag = false;
        if (n < 0)
        {
            flag = true;
            n = ~n;
        }
        double tmp = x;
        double result = 1;
        while(n)
        {
            if (n & 1) result *= tmp;
            tmp *= tmp;
            n >>= 1;
        }
        return flag ? 1.0/result/x : result;
    }
};