Python/data_structures/binary_tree/binary_search_tree.py
isidroas efaf526737
BST and RSA doctest (#8693)
* rsa key doctest

* move doctest to module docstring

* all tests to doctest

* moved is_right to property

* is right test

* fixed rsa doctest import

* Test error when deleting non-existing element

* fixing ruff EM102

* convert property 'is_right' to one-liner

Also use 'is' instead of '=='

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* child instead of children

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* remove type hint

* Update data_structures/binary_tree/binary_search_tree.py

---------

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>
2023-08-15 16:04:53 -07:00

244 lines
7.3 KiB
Python

r"""
A binary search Tree
Example
8
/ \
3 10
/ \ \
1 6 14
/ \ /
4 7 13
>>> t = BinarySearchTree()
>>> t.insert(8, 3, 6, 1, 10, 14, 13, 4, 7)
>>> print(" ".join(repr(i.value) for i in t.traversal_tree()))
8 3 1 6 4 7 10 14 13
>>> print(" ".join(repr(i.value) for i in t.traversal_tree(postorder)))
1 4 7 6 3 13 14 10 8
>>> t.remove(20)
Traceback (most recent call last):
...
ValueError: Value 20 not found
>>> BinarySearchTree().search(6)
Traceback (most recent call last):
...
IndexError: Warning: Tree is empty! please use another.
Other example:
>>> testlist = (8, 3, 6, 1, 10, 14, 13, 4, 7)
>>> t = BinarySearchTree()
>>> for i in testlist:
... t.insert(i)
Prints all the elements of the list in order traversal
>>> print(t)
{'8': ({'3': (1, {'6': (4, 7)})}, {'10': (None, {'14': (13, None)})})}
Test existence
>>> t.search(6) is not None
True
>>> t.search(-1) is not None
False
>>> t.search(6).is_right
True
>>> t.search(1).is_right
False
>>> t.get_max().value
14
>>> t.get_min().value
1
>>> t.empty()
False
>>> for i in testlist:
... t.remove(i)
>>> t.empty()
True
"""
from collections.abc import Iterable
from typing import Any
class Node:
def __init__(self, value: int | None = None):
self.value = value
self.parent: Node | None = None # Added in order to delete a node easier
self.left: Node | None = None
self.right: Node | None = None
def __repr__(self) -> str:
from pprint import pformat
if self.left is None and self.right is None:
return str(self.value)
return pformat({f"{self.value}": (self.left, self.right)}, indent=1)
@property
def is_right(self) -> bool:
return self.parent is not None and self is self.parent.right
class BinarySearchTree:
def __init__(self, root: Node | None = None):
self.root = root
def __str__(self) -> str:
"""
Return a string of all the Nodes using in order traversal
"""
return str(self.root)
def __reassign_nodes(self, node: Node, new_children: Node | None) -> None:
if new_children is not None: # reset its kids
new_children.parent = node.parent
if node.parent is not None: # reset its parent
if node.is_right: # If it is the right child
node.parent.right = new_children
else:
node.parent.left = new_children
else:
self.root = new_children
def empty(self) -> bool:
return self.root is None
def __insert(self, value) -> None:
"""
Insert a new node in Binary Search Tree with value label
"""
new_node = Node(value) # create a new Node
if self.empty(): # if Tree is empty
self.root = new_node # set its root
else: # Tree is not empty
parent_node = self.root # from root
if parent_node is None:
return
while True: # While we don't get to a leaf
if value < parent_node.value: # We go left
if parent_node.left is None:
parent_node.left = new_node # We insert the new node in a leaf
break
else:
parent_node = parent_node.left
else:
if parent_node.right is None:
parent_node.right = new_node
break
else:
parent_node = parent_node.right
new_node.parent = parent_node
def insert(self, *values) -> None:
for value in values:
self.__insert(value)
def search(self, value) -> Node | None:
if self.empty():
raise IndexError("Warning: Tree is empty! please use another.")
else:
node = self.root
# use lazy evaluation here to avoid NoneType Attribute error
while node is not None and node.value is not value:
node = node.left if value < node.value else node.right
return node
def get_max(self, node: Node | None = None) -> Node | None:
"""
We go deep on the right branch
"""
if node is None:
if self.root is None:
return None
node = self.root
if not self.empty():
while node.right is not None:
node = node.right
return node
def get_min(self, node: Node | None = None) -> Node | None:
"""
We go deep on the left branch
"""
if node is None:
node = self.root
if self.root is None:
return None
if not self.empty():
node = self.root
while node.left is not None:
node = node.left
return node
def remove(self, value: int) -> None:
# Look for the node with that label
node = self.search(value)
if node is None:
msg = f"Value {value} not found"
raise ValueError(msg)
if node.left is None and node.right is None: # If it has no children
self.__reassign_nodes(node, None)
elif node.left is None: # Has only right children
self.__reassign_nodes(node, node.right)
elif node.right is None: # Has only left children
self.__reassign_nodes(node, node.left)
else:
predecessor = self.get_max(
node.left
) # Gets the max value of the left branch
self.remove(predecessor.value) # type: ignore
node.value = (
predecessor.value # type: ignore
) # Assigns the value to the node to delete and keep tree structure
def preorder_traverse(self, node: Node | None) -> Iterable:
if node is not None:
yield node # Preorder Traversal
yield from self.preorder_traverse(node.left)
yield from self.preorder_traverse(node.right)
def traversal_tree(self, traversal_function=None) -> Any:
"""
This function traversal the tree.
You can pass a function to traversal the tree as needed by client code
"""
if traversal_function is None:
return self.preorder_traverse(self.root)
else:
return traversal_function(self.root)
def inorder(self, arr: list, node: Node | None) -> None:
"""Perform an inorder traversal and append values of the nodes to
a list named arr"""
if node:
self.inorder(arr, node.left)
arr.append(node.value)
self.inorder(arr, node.right)
def find_kth_smallest(self, k: int, node: Node) -> int:
"""Return the kth smallest element in a binary search tree"""
arr: list[int] = []
self.inorder(arr, node) # append all values to list using inorder traversal
return arr[k - 1]
def postorder(curr_node: Node | None) -> list[Node]:
"""
postOrder (left, right, self)
"""
node_list = []
if curr_node is not None:
node_list = postorder(curr_node.left) + postorder(curr_node.right) + [curr_node]
return node_list
if __name__ == "__main__":
import doctest
doctest.testmod(verbose=True)