思路：每次取中间元素，一定有一半有序，另一半部分有序，有序的部分进行二分查找，部分有序的部分递归继续处理。

class Solution {public:    int pos = -1;    int middleSearch(int left, int right,vector
     
      & nums, int target){
   //二分查找        if(left > right || right > nums.size() - 1 || left < 0)return -1;        if(nums[left] == target)return left;        int mid = (left + right) / 2;        if(nums[mid] == target)return mid;        if(target>nums[mid]) return middleSearch(mid+1,right,nums,target);        else            return middleSearch(left,mid - 1,nums,target);            }        void mixSearch(int left, int right, vector
      
       & nums, int target){
   //混合处理        if(left > right || right > nums.size() - 1 || left < 0) return;        if(nums[left] == target) {            pos = left;            return;        }        int ans;        int middle = (left + right) / 2;        if(nums[middle] > nums[right]) {            ans = middleSearch(left,middle,nums,target);            if(ans == -1) mixSearch(middle+1,right,nums,target);            else{                pos = ans;                return;            }        }        else{            ans = middleSearch(middle,right,nums,target);            if(ans == -1) mixSearch(left,middle - 1,nums,target);            else{                pos = ans;                return;            }        }    }        int search(vector
       
        & nums, int target) {        mixSearch(0,nums.size() - 1,nums,target);        return pos;    }};
       
      
     

写的冗余了点，附上简洁的代码：

class Solution {public:    int search(vector
     
      & 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]){                if(target > nums[mid] || target <= nums[r]) l = mid + 1;   // condition for pick right side                else r = mid - 1;    // else, pick left side            }else{                if(target <= nums[r] && target > nums[mid]) l = mid + 1;  // condition for pick right side                else r = mid - 1;     // else, pick left side            }         }                return -1;    }};