【二分查找】374. 猜数字大小

 1 /** 
 2  * Forward declaration of guess API.
 3  * @param  num   your guess
 4  * @return          -1 if num is lower than the guess number
 5  *                  1 if num is higher than the guess number
 6  *               otherwise return 0
 7  * int guess(int num);
 8  */
 9 
10 class Solution {
11 public:
12     int guessNumber(int n) 
13     {
14         int low = 1;
15         int high = n;
16         while (low <= high) 
17         {
18             int mid = low + (high - low) / 2;
19             int res = guess(mid);
20             if (res == 0)
21                 return mid;
22             else if (res < 0)
23                 high = mid - 1;
24             else
25                 low = mid + 1;
26         }
27         return -1;
28     }
29 };