def test_initialization_with_right_node(self):
right_node = BinaryTree.Node(1)
node = BinaryTree.Node(0, right=right_node)
assert node.key == 0
assert node.right == right_node
assert node.right.key == 1
assert not node.right._left
assert not node.right._right
assert not node.left
def test_initialization_with_left_and_right_node(self):
left_node = BinaryTree.Node(1)
right_node = BinaryTree.Node(2)
node = BinaryTree.Node(0, left_node, right_node)
assert node.key == 0
assert node.left == left_node
assert node.left.key == 1
assert not node.left._left
assert not node.left._right
assert node.right == right_node
assert node.right.key == 2
assert not node.right._left
assert not node.right._right
def _get_key_and_item(item):
if isinstance(item, BinaryTree.Node):
key = item.key
else:
key = item
item = BinaryTree.Node(key)
return key, item
def delete(self, key):
node = self.search(key)
if not node:
return False
if node.is_leaf():
if node is self.root:
self.root = None
else:
node.remove()
return True
if node.left and not node.right:
if node is self.root:
self.root = node.left
else:
node.replace(node.left)
return True
if node.right and not node.left:
if node is self.root:
self.root = node.right
else:
node.replace(node.right)
return True
if node.right and node.left:
successor = node.in_order_successor()
new_node = BinaryTree.Node(successor.key, node.left, node.right)
if node is self.root:
self.root = new_node
else:
node.replace(new_node)
successor.remove()
return True
raise Exception("Should never get here.")
def test_build_binary_tree(self):
"""
Build a tree of the following structure:
j <-- root
/ \
f k
/ \ \
a h z <-- leaves
"""
node = BinaryTree.Node
j_node = node("j")
f_node = node("f")
k_node = node("k")
a_node = node("a")
h_node = node("h")
z_node = node("z")
tree = BinaryTree(j_node)
j_node.left = f_node
j_node.right = k_node
f_node.left = a_node
f_node.right = h_node
k_node.right = z_node
assert tree.root.key == "j"
assert tree.root._left.key == "f"
assert tree.root._right.key == "k"
assert tree.root._left._left.key == "a"
assert tree.root._left._left.is_leaf()
assert tree.root._left._right.key == "h"
assert tree.root._left._right.is_leaf()
assert tree.root._right._right.key == "z"
assert tree.root._right._right.is_leaf()
def test_double_rotate_right_left(self):
"""
Test the double rotation with right-rotate followed by left-rotate.
The starting tree is on the left, the result is on the right:
1 1 2
\ \ / \
3 ===> 2 ===> 1 3
/ \
2 3
"""
root = BinaryTree.Node(1)
root.right = BinaryTree.Node(3)
root.right.left = BinaryTree.Node(2)
tree = BinaryTree(root)
tree.double_rotate_right_left(tree.root)
assert tree.root.key == 2
assert tree.root.left.key == 1
assert tree.root.right.key == 3
def test_double_rotate_left_right(self):
"""
Test a double rotation with a left-rotate followed by a right-rotate.
The starting tree is on the left, the result is on the right:
3 3 2
/ / / \
1 ===> 2 ===> 1 3
\ /
2 1
"""
root = BinaryTree.Node(3)
root.left = BinaryTree.Node(1)
root.left.right = BinaryTree.Node(2)
tree = BinaryTree(root)
tree.double_rotate_left_right(tree.root)
assert tree.root.key == 2
assert tree.root.left.key == 1
assert tree.root.right.key == 3
class TestBinaryTreeSingleRotation:
"""
A rotation of a BinaryTree changes the structure of the tree without
changing the order of the elements. The operation is used to balance
a BinarySearchTree.
"""
def setup_method(self):
"""
Build a tree with this structure
10
/ \
5 15
/ \ / \
3 8 12 18
/ \ / \
1 4 16 20
:return:
"""
root = BinaryTree.Node(10)
root.left = BinaryTree.Node(5)
root.left.left = BinaryTree.Node(3)
root.left.right = BinaryTree.Node(8)
root.left.left.left = BinaryTree.Node(1)
root.left.left.right = BinaryTree.Node(4)
root.right = BinaryTree.Node(15)
root.right.left = BinaryTree.Node(12)
root.right.right = BinaryTree.Node(18)
root.right.right.left = BinaryTree.Node(16)
root.right.right.right = BinaryTree.Node(20)
self.tree = BinaryTree(root)
def test_right_rotate(self):
"""
Test rotating the subtree starting at 5 to the right.
i.e.:
5 3
/ \ / \
3 8 ===> 1 5
/ \ / \
1 4 4 8
"""
self.tree.right_rotate(self.tree.root.left)
assert self.tree.root.key == 10
assert self.tree.root.left.key == 3
assert self.tree.root.left.left.key == 1
assert self.tree.root.left.right.key == 5
assert self.tree.root.left.right.left.key == 4
assert self.tree.root.left.right.right.key == 8
def test_left_rotate(self):
"""
Test rotating the subtree starting at 15 to the left.
i.e.:
15 18
/ \ / \
12 18 ===> 15 20
/ \ / \
16 20 12 16
"""
self.tree.left_rotate(self.tree.root.right)
assert self.tree.root.key == 10
assert self.tree.root.right.key == 18
assert self.tree.root.right.left.key == 15
assert self.tree.root.right.right.key == 20
assert self.tree.root.right.left.left.key == 12
assert self.tree.root.right.left.right.key == 16
def test_initialization_with_data(self):
node = BinaryTree.Node(0)
assert node.key == 0
assert not node.left
assert not node.right
def test_right_must_be_a_node(self):
with raises(BinaryTree.Node.ChildMustBeNodeException):
BinaryTree.Node(0, right=0)
def test_root_must_be_node(self):
with raises(BinaryTree.RootMustBeBinaryTreeNodeException):
BinaryTree(0)
def test_access_root_data(self):
root = BinaryTree.Node(0)
tree = BinaryTree(root)
assert tree.root.key == 0
def test_initialized_with_root_not_empty(self):
root = BinaryTree.Node(0)
tree = BinaryTree(root)
assert not tree.empty()
def test_node_with_neither_left_nor_right_is_leaf(self):
node = BinaryTree.Node(0)
assert node.is_leaf()
def test_node_with_right_but_not_left_is_not_leaf(self):
right_node = BinaryTree.Node(2)
node = BinaryTree.Node(0, right=right_node)
assert not node.is_leaf()
def test_node_with_left_but_not_right_is_not_leaf(self):
left_node = BinaryTree.Node(1)
node = BinaryTree.Node(0, left_node)
assert not node.is_leaf()
def setup_method(self):
"""
Build a tree with this structure
10
/ \
5 15
/ \ / \
3 8 12 18
/ \ / \
1 4 16 20
:return:
"""
root = BinaryTree.Node(10)
root.left = BinaryTree.Node(5)
root.left.left = BinaryTree.Node(3)
root.left.right = BinaryTree.Node(8)
root.left.left.left = BinaryTree.Node(1)
root.left.left.right = BinaryTree.Node(4)
root.right = BinaryTree.Node(15)
root.right.left = BinaryTree.Node(12)
root.right.right = BinaryTree.Node(18)
root.right.right.left = BinaryTree.Node(16)
root.right.right.right = BinaryTree.Node(20)
self.tree = BinaryTree(root)
def test_initialization(self):
tree = BinaryTree()
assert isinstance(tree, BinaryTree)
def test_initialization(self):
node = BinaryTree.Node()
assert isinstance(node, BinaryTree.Node)
assert not node.key
assert not node.left
assert not node.right
def test_initialized_tree_is_empty(self):
tree = BinaryTree()
assert tree.empty()