leetcode算法题--数值的整数次方

原题链接：https://leetcode-cn.com/problems/shu-zhi-de-zheng-shu-ci-fang-lcof/

double myPow(double x, int n) {
     
    if (x == 0) return 0;
    long b = n;
    double res = 1.0;
    if (b < 0) {
     
        x = 1 / x;
        b = -b;
    } 
    while (b > 0) {
     
        if ((b & 1) == 1) res *= x;
        x *= x;
        b >>= 1;
    }
    return res;
}