540. Single Element in a Sorted Array

class Solution {
    public int singleNonDuplicate(int[] arr)
     {
        int n= arr.length;
        if(n==1) 
        return arr[0]; 
        
        if(arr[0] != arr[1])
         return arr[0];
          
      if(arr[n-1] != arr[n-2]) 
      return arr[n-1];

     int low = 1, high = n - 2;
     
     while(low <= high) 
     {
        int mid = (low + high) / 2;
        
        if(arr[mid] != arr[mid+1] && arr[mid] != arr[mid-1])
         {
           return arr[mid];
         }


       // we are in left
       if((mid % 2 == 1 && arr[mid] == arr[mid-1]) || (mid % 2 == 0 && arr[mid] == arr[mid+1] ))
        {
         low = mid + 1;
        }

        // we are on right
        else 
        { 
          high = mid - 1;
}
}
      return -1;

        
    }
}