154. Find Minimum in Rotated Sorted Array II

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]).

Find the minimum element.

The array may contain duplicates.

Example 1:

Input: [1,3,5]
Output: 1

Example 2:

Input: [2,2,2,0,1]
Output: 0

Note:

• This is a follow up problem to Find Minimum in Rotated Sorted Array.

• Would allow duplicates affect the run-time complexity? How and why?

// Binary Search
int findMin(vector<int>& nums) { // time: O(logn); space: O(1)
    if (nums.empty()) return -1;
    int left = 0, right = nums.size() - 1;
    while (left < right) {
        if (nums[left] < nums[right]) { // no rotation in [left, right]
            break;
        }
        int mid = left + (right - left) / 2;
        if (nums[left] < nums[mid]) { // [left, mid] is sorted
            left = mid + 1;
        } else if (nums[left] > nums[mid]) { // [mid + 1, right] is sorted
            right = mid;
        } else {
            ++left;
        }
    }
    return nums[left];
}

153. Find Minimum in Rotated Sorted Array