You are given a sorted array consisting of only integers where every element appears exactly twice, except for one element which appears exactly once. Return the single element that appears only once. Your solution must run in O(log n) time and O(1) space.
Example 1
Input: nums = [1,1,2,3,3,4,4,8,8]
Output: 2
Explanation: Every value comes in a pair (1 1, 3 3, 4 4, 8 8) except 2, which appears once.
Example 2
Input: nums = [3,3,7,7,10,11,11]
Output: 10
Explanation: 3, 7 and 11 each appear twice, and 10 appears only once.
Example 3
Input: nums = [1]
Output: 1
Explanation: The only element is the single one.
Before the single element, pairs start at even indices (0-1, 2-3, ...). After it, that parity breaks. Binary search for where the even-index pairing first fails.
Run checks all cases above. Submit evaluates all test cases.