不理解Search in Rotated Sorted Arra

class Solution {
public:
    bool search(vector<int>& nums, int target) {
       if(nums.empty()) return false;
        int start = 0;
        int end = nums.size() - 1;
        while(start + 1 < end){
            int mid = start + (end - start) / 2;
            if(nums[mid] == target) return true;
            if(nums[mid] > nums[start]){
                if(  target >= nums[start]&& target <= nums[mid]  ){
                    end = mid;
                }
                else start = mid;
            }
            else if(nums[mid] < nums[start]){
                if(target >= nums[mid] && target <= nums[end]){
                    start = mid;
                }
                else{
                    end = mid;
                }
            }
            else{
                start++;
            }
        }
        if(nums[start] == target) return true;
        if(nums[end] == target) return true;
        return false;
    }
};