leetcode374

We are playing the Guess Game. The game is as follows:

I pick a number from 1 to n. You have to guess which number I picked.

Every time you guess wrong, I'll tell you whether the number is higher or lower.

You call a pre-defined API guess(int num) which returns 3 possible results (-1, 1, or 0):

-1 : My number is lower
1 : My number is higher
0 : Congrats! You got it!
Example :

Input: n = 10, pick = 6
Output: 6

是最基本的二分法，不赘述了，纯练模板避免手生。start+1<end, 最后盼两个。

实现：

    /* The guess API is defined in the parent class GuessGame.
   @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 Solution extends GuessGame {
        public int guessNumber(int n) {
            int start = 1;
            int end = n;
            while (start + 1< end) {
                int mid = start + (end - start) / 2;
                int answer = guess(mid);
                if (answer == 0) {
                    return mid;
                } else if (answer < 0){
                    end = mid;
                } else {
                    start = mid;
                }
            }
            if (guess(start) == 0) {
                return start;
            }
            return end;
        }
    }