总结：二分法题目汇总 以及二分法模板

 1         while (l < r - 1) {
 2             int m = l + (r - l) / 2;
 3             
 4             // means that there is no rotate.
 5             ... 这里添加各种退出条件，比如找到了目标值等 8             
 9             // left side is sorted.
10             if (A[m] > A[l]) {
11                 l = m;
12             } else {
13                 r = m;
14             }
15         }