sword to offer 009

class  {
private:
    int Pow(int number, int pow) {
        int res = 1;
        while(pow) {
            if(pow & 1) {
               res *= number;
            }
            number *= number;
            pow >>= 1;
        }
        return res;
    }
public:
    int jumpFloorII(int number) {
        return Pow(2, number - 1);
    }
};