LeetCode: Pow(x, n)

Implement pow(x, n).

   double powPos(double x, long long n) {  
     if(n == 0)return 1;  
     if(n == 1)return x;  
     double a = powPos(x,n/2);  
     return (a*a*powPos(x, n%2));  
   }  

   double pow(double x, int n) {  
     long long ln = (long long)n;  
     double res = powPos(x,abs(ln));  
     if(n<0)res = (double)1.0/res;  
     return res;  
   }