### LeetCode Challenge #540. Single Element in a Sorted Array

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:

• `1 <= nums.length <= 105`
• `0 <= nums[i] <= 105`
##### Video Solution
###### Java Solution
```				```
class Solution {
public int singleNonDuplicate(int[] nums) {
if(nums.length==1){
return nums[0];
}else if ( nums[0]!=nums[1]){
return nums[0];
}else if ( nums[nums.length-1] != nums[nums.length-2]){
return nums[nums.length-1];
}

int start = 0 ;
int end = nums.length-1 ;

while(start<=end){
int mid = (start + end)/2;

if(nums[mid]!=nums[mid-1] && nums[mid]!=nums[mid+1]){
return nums[mid];
}else if ( mid % 2 ==1 ){ // if mid index is odd

if(nums[mid-1]==nums[mid]){
start = mid+1 ;
}else{
end = mid-1 ;
}
}else { // if mid index is even
if(nums[mid]==nums[mid+1]){
start = mid +1 ;
}else{
end = mid -1 ;
}
}
}

return -1 ;
}
}
```
```