Single Element in a Sorted Array

Single Element in a Sorted Array. Find the element that appears once in a sorted array where every other element appears twice.

Given a sorted array of integers. In this array, every element appears twice except one element which appears only once. Write a code to find the element which appears only once.

For example:

Example 1:

Input: [1, 1, 2, 2, 3, 4, 4, 7, 7]

Output: 3

Except 3 every other element appears twice.

Example 2:

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

NOTE – Try to solve this problem in O(logn) time complexity and by using constant space O(1).