这道老题思路应该很透彻了。一开始分nums[mid] == target和nums[mid]可能掉入两大段讨论：
image.png
然后在两大段每一段里面又可以具体分析成两种情况：
image.png
最后检查一下start 和end index的元素是不是target就可以
class Solution {
public int search(int[] nums, int target) {
if (nums == null || nums.length == 0){
return -1;
}
int start = 0;
int end = nums.length - 1;
while (start + 1 < end){
int mid = start + (end - start) / 2;
if (nums[mid] == target){
return mid;
} else if (nums[mid] > nums[start]){
if (target >= nums[start] && target <= nums[mid]){
end = mid;
} else {
start = mid;
}
} else if (nums[mid] < nums[end]){
if (target >= nums[mid] && target <= nums[end]){
start = mid;
} else {
end = mid;
}
}
}
if (nums[start] == target){
return start;
}
if (nums[end] == target){
return end;
}
return -1;
}
}
