LintCode 662. 猜数游戏

 1 // Forward declaration of guess API.
 2 // @param num, your guess
 3 // @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
 4 int guess(int num);
 5 
 6 class Solution {
 7 public:
 8     /**
 9      * @param n an integer
10      * @return the number you guess
11      */
12     int guessNumber(int n) {
13         // Write your code here
14         int start = 1;
15         int end = n;
16         int res = start + (end - start)/2;//取中间值需要写成这样
17         while(1){
18             int ret = guess(res);
19             if(!ret) break;
20             else if(ret == 1) start = res+1;
21             else end = res-1;
22             res = start + (end - start)/2;
23         }
24         return res;
25     }
26 };