1 class Solution {
 2 public:
 3     double Power(double b, int e) {
 4         int p = abs(e);
 5         double r = 1.0;
 6         while (p) {
 7             if (p & 1) r *= b;
 8             b *= b;
 9             p >>= 1;
10         }
11         return e > 0 ? r : 1 / r;
12     }
13 };