class Solution {public:    double pow(double x, int n) {           double result =1;		   int    index = abs(n);			   		  for(int i=0; i<32;i++)		  {				  if(0x01<<i & index)				  {					 result *=ppow(x,i);				  }		  }		  if(n <0)		  	result = 1/result;		   		              return result;		             }     double ppow(double x,int n)     {	    double result =x;		while(n > 0)		{			n =n-1;			result = result * result;		}        return result;     }    };