new_contents: post = [ 5, 6, 3, 1, 4, 2, 7 ]
  ino =  [ 7, 5, 6, 2, 3, 1, 4 ]
  # ino = [2, 1, 3]
  # post = [2, 3, 1]
  class Node(object):
      def __init__(self, val):
          self.val = val
          self.left = None
          self.right = None
          
  def construct(post, ino):
      if not post or not ino:
          return
      root = Node(post[-1])
      
      idx = ino.index(root.val)
      root.left = construct(post[:idx], ino[:idx])
      root.right = construct(post[idx:len(post)-1], ino[idx+1:])
      return root
      
  Tree = construct(post, ino)
  
subject: Create construct_binary_tree_from_in_order_n_post_order.py