text: #!/usr/bin/env python3
  
  """Find the element that appears once in sorted array.
  
  Given a sorted array A, size N, of integers; every element appears twice except for one. Find that element 
  in linear time complexity and without using extra memory.
  
  Source:
  https://practice.geeksforgeeks.org/problems/find-the-element-that-appears-once-in-sorted-array/0
  """
  
  
  def find_unique_value(items: list):
      """Find the element that appears once in sorted array."""
      unique = -1
      for index, i in enumerate(items):
          # Set the unique value. Continue to next i value.
          if unique < 0:
              unique = i
              continue
          # If duplicate found and next is different, reset to -1.
          if unique == i and i != items[index + 1]:
              unique = -1
          # Since list is sorted, once unique is greater than 0
          # and i is less than unique break from loop.
          if unique > 0 and unique < i:
              break
      return unique
  
  
  def main():
      print(find_unique_value(
          items=[1, 1, 1, 2, 2, 2, 3, 3, 4, 50, 50, 65, 65, ]))
  
  
  if __name__ == "__main__":
      main()
  