374.guess number higher or lower

   @param num, your guess
   @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
      int guess(int num); */
public class  extends GuessGame {
    public int guessNumber(int n) {
        int start = 1, end = n;
        while(start < end){
            //int mid = (start + end) / 2;
            int mid = i + (j - i) / 2;
            if(guess(mid)==0)
                return mid;
            else if(guess(mid)==1)
                start = mid + 1;
            else
                end = mid;       
        }
        return start;
    }
}

int mid = (start + end) / 2;