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)