class Test3AVLDoubleLeftRight(unittest.TestCase):
def setUp(self):
A = BSTNode(3, "A")
B = BSTNode(1, "B")
C = BSTNode(2, "C")
B.right = C
A.left = B
# A
# /
# B
# \
# C
self.tree = AVL()
self.nodes = (A, B, C)
def test1_double_left_right_rotation_returns_new_node(self):
"""Calling double_left_right_rotation for a node returns the new node which takes the place of the old node. (1p)"""
A, _, C = self.nodes
self.assertIs(
self.tree.double_left_right_rotation(A),
C,
"Rotating a node {0} with a LR rotation should return the node which takes its place."
.format(A)
)
def test2_double_left_right_rotation(self):
"""Rotating a node A with a double, left-right rotation moves the left child of A as the new left child of the old right child of the old left child of A. (1p)"""
A, B, C = self.nodes
A_new = self.tree.double_left_right_rotation(A)
self.assertIs(
C.left,
B,
"The left child of {0} should be {1}."
.format(C.left, B)
)
self.assertIs(
A_new,
C,
"Calling tree.double_left_right_rotation({0}) should return {1}."
.format(A_new, C)
)
self.assertIs(
C.right,
A,
"The right child of {0} should be {1}."
.format(C.right, A)
)
def test3_double_left_right_rotation_updates_height(self):
"""After rotating a node A with a double, left-right rotation, the heights of the nodes are correct. (1p)"""
A, B, C = self.nodes
self.tree.double_left_right_rotation(A)
expected_node_heights = [
(A, 0),
(B, 0),
(C, 1),
]
for node, expected_height in expected_node_heights:
node_height = node.height()
self.assertEqual(
node_height,
expected_height,
"The height of {0} should be {1}, not {2}."
.format(node, expected_height, node_height)
)
