[LeetCode]--Pow(x,n)

public class Solution {
    public double pow(double x, int n) {
         if(n<0){
            return 1.0/powHelper(x,n);
        }else{
            return powHelper(x, n);
        }
    }
    
    public double powHelper(double x, int n){
       if(n == 0){
            return 1;
        }
        
        double v = powHelper(x, n/2);
        
        if(n % 2 == 0){
            return v*v;
        }else{
            return v*v*x;
        }
    }
}