LeetCode-Pow

class Solution {
public:
    double pow(double x, int n) {
            if(n==1)return x;
        else if(n==-1)return 1/x;
        else if(n==0)return 1;
        else{
            bool flag=n>0;
            if(!flag)n=-n;
            double ret=1;
            int bit=0x40000000;
            for(int i=0;i<31;i++){
                if(n&bit){
                    ret=ret*ret*x;
                }
                else{
                    ret=ret*ret;
                }
                bit/=2;
            }
            if(!flag)return 1/ret;
            return ret;
        }
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
    }
};