def test_delete_single_rotation(insert, delete, expected):
"""Tests deletion resulting in a single rotation."""
tree = AVLTree(insert)
tree.delete(delete)
assert delete not in tree
assert pre_order(tree) == expected
assert_avl_invariants(tree.root)
def test_delete_reattach():
"""Removing the root from a 2-depth V should reattach nodes correctly."""
tree = AVLTree([3, 2, 4, 1, 5])
tree.delete(3)
assert 3 not in tree
assert pre_order(tree) == [2, 1, 4, 5]
assert_avl_invariants(tree.root)
def test_delete_trivial(insert, delete, expected):
"""Tests deletion of root/leaf nodes requiring no rotation."""
tree = AVLTree(insert)
tree.delete(delete)
assert delete not in tree
assert pre_order(tree) == expected
assert_avl_invariants(tree.root)
def test_delete_rotation_under_root(insert, delete):
tree = AVLTree(insert)
tree.delete(delete)
assert delete not in tree
expected = sorted(insert)
expected.remove(delete)
assert in_order(tree) == expected
assert_avl_invariants(tree.root)
def test_delete_attach_without_rotation(insert, deletes, expected):
"""Tests selective pruning of nodes and reattaching them to parents."""
tree = AVLTree(insert)
for key in deletes:
tree.delete(key)
assert key not in tree
assert pre_order(tree) == expected
assert_avl_invariants(tree.root)
def test_two_way_rotations_with_subtree_at_pivot(insert, delete):
"""Deletion causes a LR or RL rotation and the new subtree root has children."""
tree = AVLTree(insert)
tree.delete(delete)
assert delete not in tree
expected = sorted(insert)
expected.remove(delete)
assert in_order(tree) == expected
assert_avl_invariants(tree.root)
def test_delete_double_rotation():
"""Tests deletion resulting in a double rotation."""
tree = AVLTree([16, 8, 24, 4, 12, 20, 28, 2, 6, 10, 32, 1, 3])
tree.delete(20)
assert 20 not in tree
assert tree.root.value == 8
assert tree.root.left.value == 4
assert tree.root.right.value == 16
assert_avl_invariants(tree.root)
def test_delete_root():
"""Tests deletion of singular root node."""
tree = AVLTree([1])
tree.delete(1)
assert 1 not in tree
assert tree.root is None
def test_delete_nonexisting():
"""Tests deletion of nonexisting key raises KeyError."""
tree = AVLTree()
with pytest.raises(KeyError):
tree.delete(2)