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 here17         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 };