class Solution {
    public double myPow(double x, int n) {
        long b = n;  // n=−2147483648 时执行 n = −n 会因越界而赋值出错
        if(n < 0){
            x = 1 / x;
            b = -b;
        }
        double res = 1;
        while(b != 0){
            if((b & 1) == 1) res *= x;
            x *= x;
            b >>= 1;
        }
        return res;
    }
}