leetcode 50. Pow(x, n)

class Solution {
public:
    double myPow(double x, int n) {
        if(n==0) return 1;
        if(n<0)
            return 1/myPow(x,-n);
        if(n&1==0)
            return myPow(x*x,n/2);
        return x*myPow(x,n-1);
    }
};

class Solution {
public:
    double myPow(double x, int n) {
        double res=1.0;
        int p=n;
        while(p){
            if(p&1==1)
                res*=x;
            p/=2;if(p==0) break;
            x*=x;
        }
        return n>0?res:1/res;
    }
};