``````class Solution {
public:
int search(vector<int>& nums, int target) {
int l = 0,r = nums.size() - 1;
while(l <= r)
{
int mid = l + (r - l)/2;
if(nums[mid] == target) return mid;
if(nums[mid] < nums[r])
{
//后半段有序
if(nums[mid] < target && target <= nums[r])
l = mid + 1;
else
r = mid - 1;
}else{
//前半段有序
if(nums[l] <= target && target < nums[mid])
r = mid - 1;
else
l = mid + 1;
}
}

return -1;
}
};``````
``````class Solution {
public:
int search(vector<int>& nums, int target) {
int l = 0,r = nums.size() - 1;
while(l <= r)
{
int mid = l + (r - l)/2;
if(nums[mid] == target) return mid;
if(nums[mid] > nums[r])
{
//前半段有序,且target位于前半段
if(nums[l] <= target && target < nums[mid])
r = mid - 1;
else
l = mid + 1;
}else{
//后半段有序,且target位于后半段
if(nums[mid] < target && target <= nums[r])
l = mid + 1;
else
r = mid - 1;
}
}
return -1;
}
};``````

2021.06.10更新另一种思路：

``````class Solution {
public:
int search(vector<int>& nums, int target) {
int l = 0,r = nums.size() -1;
while(l <= r)
{
int mid = l + (r-l)/2;
if(nums[mid] == target) return mid;
//[3,4,5,1,2]
if(nums[mid] > nums[r])
{
if(target < nums[mid] && target >= nums[l])
r = mid - 1;
else
l = mid + 1;
//[5,1,2,3,4]
}else if(nums[mid] < nums[l]){
if(target > nums[mid] && target <= nums[r])
l = mid + 1;
else
r = mid - 1;
}else{
if(target < nums[mid])
r = mid -1;
else
l = mid + 1;
}
}
return -1;
}
};``````