实现sqrt()函数

  int mySqrt(int x) {

        if(x == 0)
         {
           return 0;
         }        
         int ans = exp(0.5*log(x));
         int k = ans+1;
         //int r = k*k;
         if((long long) k*k <=x)
         {
              return k;
         }
         else
         {
              return ans;
         }
    }