def test_parent(self):
tree = LinkedBinaryTree()
tree._add_root(0)
root = tree.root()
tree._add_left(root, 1)
left = tree.left(root)
parent = tree.parent(left)
self.assertEqual(parent, root)
class Tree(object):
""" General tree implementation adapting a binary tree."""
# constructor
def __init__(self):
self._binary_tree = LinkedBinaryTree()
# public accessor
def root(self):
""" Return Position representing the tree's root (or None if empty)."""
return self._binary_tree.root()
def parent(self, p):
""" Return the Position of p's parent (or None if p is root)."""
father = self._binary_tree.parent(p)
child = p
while self._binary_tree.right(father) is child:
child = father
father = self._binary_tree.parent(child)
return father
def num_children(self, p):
""" Return the number of children of Position p."""
count = 0
if self._binary_tree.left(p):
child = self._binary_tree.left(p)
while child:
count += 1
child = self._binary_tree.right(child)
return count
def children(self, p):
""" Generate an iteration of Positions representing p's children."""
if self._binary_tree.left(p):
child = self._binary_tree.left(p)
while child:
yield child
child = self._binary_tree.right(child)
def __len__(self):
""" Return the total number of elements in the tree."""
return len(self._binary_tree)
def __str__(self):
""" str representation of linked binary tree."""
s = ''
for item in self:
s += str(item)
return s
def is_root(self, p):
""" Return True if Position p represents the root of the tree."""
return self.root() == p
def is_leaf(self, p):
""" Return True if Position p does not have any children."""
return self.num_children(p) == 0
def is_empty(self):
""" Return True if the tree is empty."""
return len(self) == 0
def depth(self, p):
""" Return the number of levels separating Position p from the root."""
if self.is_root(p):
return 0
elif self._binary_tree.right(self.parent(p)) == p:
return self.depth(self.parent(p))
else:
return 1 + self.depth(self.parent(p))
def _height(self, p):
""" Return the height of the subtree rooted at Position p."""
if self.is_leaf(p):
return 0
else:
return 1 + max(self._height(c) for c in self.children(p))
def height(self, p=None):
if p is None:
p = self.root()
return self._height(p)
def __iter__(self):
""" Generate an iteration of the tree's elements."""
for p in self.positions():
yield p.element()
def positions(self):
""" Generate an iteration of the tree's positions."""
return self.preorder() # return entire preorder iteration
def preorder(self):
""" Generate a preorder iteration of positions in the tree."""
return self._binary_tree.preorder()
def postorder(self):
""" Generate a postorder iteration of positions in the tree."""
return self._binary_tree.inorder()
def breadthfirst(self):
""" Generate a breadth-first iteration of the positions of the tree."""
return self._binary_tree.breadthfirst()
# nonpublic mutators
def _add_root(self, e):
""" Place element e at the root of an empty tree and return new
Position. Raise ValueError if tree nonempty.
"""
return self._binary_tree._add_root(e)
def _add_child(self, p, e):
""" Create a new child for Position p, storing element e."""
left = self._binary_tree.left(p)
if left is not None:
return self._binary_tree._add_right(left, e)
else:
return self._binary_tree._add_left(p, e)
def _replace(self, p, e):
""" Replace the element at position p with e, and return old
element."""
return self._binary_tree._replace(p, e)
def _delete(self, p):
"""Delete the node at Position p, and replace it with its child, if
any.
:return : the element that had been stored at Position p.
:raise : ValueError if Position p is invalid or p has two children.
"""
if self.num_children(p) > 1:
raise ValueError('Position has more than one child')
elif self.num_children(p) == 0:
self._binary_tree._delete(p)
else:
child = self._binary_tree.left(p)._node
if p == self.root():
self._binary_tree._root = p._node
else:
parent = self.parent(p)._node
parent._left = child
child._parent = parent
self._binary_tree._size -= 1
p._node._parent = p._node
return p.element()
def _attach(self, p, t_list):
""" Attach trees storing in t_list to the external Position p in the
order with t_list itself. As a side effect, trees in t_list will be set
to empty.
:raise : TypeError if trees in t_list do not match type of this tree
:raise : ValueError if Position p is invalid or not external.
"""
if not t_list:
return
if self._binary_tree.left(p) is None:
t1 = t_list.pop(0)
if not type(self) is type(t1):
raise TypeError('Tree types must match')
t2 = LinkedBinaryTree()
self._binary_tree._force_attach(p, t1._binary_tree, t2)
left = self._binary_tree.left(p)
for t2 in t_list:
if type(t2) is not type(self):
raise TypeError('Tree types must match')
t1 = LinkedBinaryTree()
self._binary_tree._force_attach(left, t1, t2._binary_tree)
return