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:
n = 10, I pick 6.
Return 6.

思路：

二分查找。

int guess(int num);
     int guessNumber(int n)
     {
         int maxnum = n, minnum = 1;
         while (1)
         {
             int mid = minnum + (maxnum - minnum) / 2;
             int gus = guess(mid);
             if (gus == 0)return mid;
             if (gus == 1)
             {
                 minnum = mid + 1;
             }
             else maxnum = mid - 1;
         }         
          
     }

[leetcode-374-Guess Number Higher or Lower]