text: x = [20, 10, 5, 9, 15, 17, 7]
  
  class Node:
      def __init__(self, key = None):
          self.key = key
          self.parent = None
          self.left = None
          self.right = None
  
  NodeArr = [Node for x in range(100)]
  
  def completeBT(arr, n):
      for i in range(n):
  
  