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];
}