[LintCode] 第一个错误的代码版本

 1 /**
 2  * class VersionControl {
 3  *     public:
 4  *     static bool isBadVersion(int k);
 5  * }
 6  * you can use VersionControl::isBadVersion(k) to judge whether 
 7  * the kth code version is bad or not.
 8 */
 9 class Solution {
10 public:
11     /**
12      * @param n: An integers.
13      * @return: An integer which is the first bad version.
14      */
15     int findFirstBadVersion(int n) {
16         // write your code here
17         int l = 1, r = n;
18         while (l < r) {
19             int m = (l + r) / 2;
20             if (VersionControl::isBadVersion(m)) r = m;
21             else l = m + 1;
22         }
23         return l;
24     }
25 };