LeetCode: Pow(x, n) [049]

class Solution {
public:
    double pow(double x, int n) {
        if(x==0)return 0;   //两种特殊情况
        if(n==0)return 1;
        
        
        double result=1;
        bool isNegative= n<0?true:false;
        long long nTotal= isNegative? -1*n : n;
        long long nUsed=1;
        long long nUsedTotal=0;
        double multiply=x;
        
        while(nUsedTotal<nTotal){
            nUsed=1;
            multiply=x;
            while(nUsed*2<nTotal-nUsedTotal){
                nUsed*=2;
                multiply = multiply*multiply;
            }
            nUsedTotal+=nUsed;
            result*=multiply;
        }
        if(isNegative) return 1/result;
        return result;
    }
};