def insert(self, value):
'''Insert a new BTNode with value value into this BST. Do not insert
duplicates.
'''
if self._root is None:
self._root = BTNode(value)
return self
return _insert(self._root, BTNode(value))
def __init__(self, value, colour=BLACK, left=None, right=None,
parent=None):
'''Init a RBTNode with value value, colour colour, parent parent, left
child left, and right child right.
'''
BTNode.__init__(self, value, left, right)
self.colour = colour
self.parent = parent
def _delete_node(node, parent):
'''Remove the BTNode node from the tree rooted at BTNode.
Pre: parent is the BTNode parent of node
node is not None
Hint: this is where you use get_min
'''
# leaf is included in this case; where node.left == None
if node.right is None:
_update_parent(node, parent, node.left)
# Need to delete the min node and update parent
else:
min_value = _get_min(node.right)
substitute = BTNode(min_value)
_delete(node, min_value, parent)
substitute.left = node.left
substitute.right = node.right
_update_parent(node, parent, substitute)
def delete(self, value):
'''Delete a BTNode that contains value value from this BST. If there
is no such BTNode, raise a NoSuchValueException.
'''
# special case: empty tree
if self._root is None:
raise NoSuchValueException
# special case: deleting a root
if self._root.value == value:
# create a fake root (use min - 1 as value), then remove root
fake_root = BTNode(_get_min(self._root) - 1)
fake_root.right = self._root
_delete(fake_root, self._root.value, None)
self._root = fake_root.right
else:
_delete(self._root, value, None)
def random_insert(node, value):
'''Return node with value insterted randomly into a subtree rooted at node;
insertion at leaf level;
at each level, go right with prob 50% and left with prob 50%.'''
# use random.random() to decide left or right
if node is None:
return BTNode(value)
# Insert to the left is > 0.5
if random.random() > 0.5:
if node.left is None:
node.left = BTNode(value)
else:
random_insert(node.left, value)
else:
if node.right is None:
node.right = BTNode(value)
else:
random_insert(node.right, value)
return node
def delete(self, value):
'''Delete a BTNode that contains value value from this BST. If there
is no such BTNode, raise a NoSuchValueException.
'''
# this one will take a bit longer :)
# special case: empty tree
if self._root is None:
raise NoSuchValueException
# special case: deleting a root
if self._root.value == value:
# create a fake root (use min - 1 as value), then remove root
fake_root = BTNode(_get_min(self._root) - 1)
fake_root.right = self._root
_delete(fake_root, self._root.value, None)
self._root = fake_root.right
else:
_delete(self._root, value, None)
# Still don't understand why case 1 doesn't work
"""
'''Delete a BTNode that contains value value from this BST. If there
is no such BTNode, raise a NoSuchValueException.
'''
# this one will take a bit longer :)
pass
class NoSuchValueException(Exception):
pass
if __name__ == '__main__':
BT = BST(
BTNode(5, BTNode(3, BTNode(2, BTNode(1), None), BTNode(4)),
BTNode(6, None, BTNode(7))))
# the string shuld be '\n\t\t7\n\n\t6\n\n5\n\n\t\t4\n\n\t3\n\n\t\t2\n\n\t\t\t1\n'
print(BT)
print(BT.preorder())
print(BT.inorder())
print(BT.postorder())
print(BT.is_bst())
print(BT.size())
print(BT.fringe())
print(BT.height())
print(20 * '=')
for x in (0, 4.5, 10):
BT.insert(x)
print(BT)
def __str__(self):
'''Return a str representation of this RedBlackTree.'''
return '{}: {}'.format(BTNode.__str__(self), 'Red' if self.colour == RED else 'Black')