540\. Single Element in a Sorted Array

Medium

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

**Example 2:**

**Input:** nums = [3,3,7,7,10,11,11]

**Output:** 10

**Constraints:**

*   <code>1 <= nums.length <= 10<sup>5</sup></code>
*   <code>0 <= nums[i] <= 10<sup>5</sup></code>