0440949 Andreas van Cranenburgh
Opdracht 4 Datastructuren

R 6.9. No. This is not possible, cause otherwise the very terms "preorder" and
"postorder" would be quite silly. Imagine this tree:

   A
B     C

preorder traversal gives the sequence: [A, B, C]
postorder traversal gives the sequence: [B, C, A]

 - a tree with one root and one leaf will give similar results (different
   order).
 - a tree with even more nodes than this example will show even more different
   order.
So I consider the point proven.

R 6.10. I believ my answer was generalized enough to apply to proper binary
trees as well.

C 6.5: Such a tree could look like this:

         a
       /   \
      b     c
    /   \
   d     e

C 6.10. General Euler Tour, an informal description:

- From rootnode, start with the first child and visit all its left-most
  children, until we reach the bottom.
- Now re-visit visited nodes, while also visiting all their children, starting
  from left going to right, until we reach the root node again.
- Upon reaching the rood node, go to the next child of the root node and go
  down and up again as already described.

Attempt at code (but unfinished):

def GenericEulerTour(tree):
	"""Implements an Euler Tour for Ordered Trees"""
	result = [tree.root]	#We return a sequence, add root first.
	for a in root.children:
		b = a.getLeftMostChild()
		result.add(b)
		while b.hasChild():
			b = b.getLeftMostChild()
			result.add(b)

		while b.hasParent():
			b = b.parent()
			result.add..
		# !!! .... incomplete .... !!!
	return result
	
def getLeftMostChild(Node):
	# the children accesor method returns an ordered sequence of all
	# children, so return first
	return Node.children[0]

P 6.4. Draw binary tree: see attached file.