33. Search in Rotated Sorted Array 在旋转的排序数组中查找元素

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Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.

(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).

You are given a target value to search. If found in the array return its index, otherwise return -1.

You may assume no duplicate exists in the array.

解题思路：

利用改进的二分查找搜索。

             

class Solution {
public:
    int search(vector<int>& nums, int target) {
        int begin = 0;
        int end = nums.size() - 1;
        
        while(begin <= end)
        {
            int mid = (begin + end) / 2;
            cout << mid << " " << target << endl;
            if(nums[mid] == target)
                return mid;
            else if(nums[mid] < target)
            {
                if(nums[mid] >= nums[begin])      （5）
                    begin = mid + 1;
                else if(nums[mid] < nums[begin])
                {
                    if(target >= nums[begin])     （3）
                        end = mid - 1;
                    else if(target < nums[begin]) （1）
                        begin = mid + 1;
                }
                else
                    end = mid - 1;
            }
            else if(nums[mid] > target)
            {
                if(nums[mid] > nums[begin])        
                {
                    if(target >= nums[begin])       （4）
                        end = mid - 1;
                    else if(target < nums[begin])   （6）
                        begin = mid + 1;
                }
                else if(nums[mid] < nums[begin])    （2）
                    end = mid - 1;
                else
                    begin = mid + 1;
            }
        }
        
        return -1;
    }
};