[LeetCode] 81. Search in Rotated Sorted Array II

[LeetCode] 81. Search in Rotated Sorted Array II

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Follow up for “Search in Rotated Sorted Array”:
What if duplicates are allowed?

Would this affect the run-time complexity? How and why?

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).

Write a function to determine if a given target is in the array.

The array may contain duplicates.

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類似33題，列表是有序的環，而且有重複元素的時候怎麼辦。
二分查找，判斷 l-m 是有序的還是 m-r 是有序的，然後判斷target是否在有序的裏面，再去處理l、r與m的關係。

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