数值的整数次方

class Solution {
public:
double Power(double base, int exponent) {
double res=1.0;
if(base==1||exponent==0) return 1;
if(base==0) return 0;
if(exponent<0) base=1/base;
exponent=abs(exponent);
while(exponent!=0){
if(exponent%2==1) res=res*base;
base=base*base;
exponent=exponent/2;
}
return res;

}
};