540. Single Element in a Sorted Array

class Solution {
    public int singleNonDuplicate(int[] nums) {
      int start = 0;
      int end = nums.length - 1;
      while (start < end){
        int mid = start + (end - start)/2;
        
        if(mid % 2 == 1){
          mid--;
        }
        
        if(nums[mid] != nums[mid+ 1]){
          end = mid;
        }else{
          start = mid + 2;
        }
      }
      return nums[start];     
    }
}

 

Given a sorted array consisting of only integers where every element appears twice except for one element which appears once. Find this single element that appears only once.

Example 1:

Input: [1,1,2,3,3,4,4,8,8]
Output: 2

 

Example 2:

Input: [3,3,7,7,10,11,11]
Output: 10

 

Note: Your solution should run in O(log n) time and O(1) space.