153. Find Minimum in Rotated Sorted Array

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.

You may assume no duplicate exists in the array.

Example 1:

Input: [3,4,5,1,2] 
Output: 1

Example 2:

Input: [4,5,6,7,0,1,2]
Output: 0

// 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]) { // 1st half is sorted
            left = mid + 1;
        } else { // 2nd half is sorted
            right = mid;
        }
    }
    return nums[left];
}

154. Find Minimum in Rotated Sorted Array II