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"""

A binary search Tree

"""

class Node:

def __init__(self, value, parent):

self.value = value

self.parent = parent # Added in order to delete a node easier

self.left = None

self.right = None

def __repr__(self):

from pprint import pformat

if self.left is None and self.right is None:

return str(self.value)

return pformat({"%s" % (self.value): (self.left, self.right)}, indent=1)

class BinarySearchTree:

def __init__(self, root=None):

self.root = root

def __str__(self):

"""

Return a string of all the Nodes using in order traversal

"""

return str(self.root)

def __reassign_nodes(self, node, newChildren):

if newChildren is not None: # reset its kids

newChildren.parent = node.parent

if node.parent is not None: # reset its parent

if self.is_right(node): # If it is the right children

node.parent.right = newChildren

else:

node.parent.left = newChildren

else:

self.root = newChildren

def is_right(self, node):

return node == node.parent.right

def empty(self):

return self.root is None

def __insert(self, value):

"""

Insert a new node in Binary Search Tree with value label

"""

new_node = Node(value, None) # 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

while True: # While we don't get to a leaf

if value < parent_node.value: # We go left

if parent_node.left == 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 == None:

parent_node.right = new_node

break

else:

parent_node = parent_node.right

new_node.parent = parent_node

def insert(self, *values):

for value in values:

self.__insert(value)

return self

def search(self, value):

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=None):

"""

We go deep on the right branch

"""

if node is None:

node = self.root

if not self.empty():

while node.right is not None:

node = node.right

return node

def get_min(self, node=None):

"""

We go deep on the left branch

"""

if node is None:

node = self.root

if not self.empty():

node = self.root

while node.left is not None:

node = node.left

return node

def remove(self, value):

node = self.search(value) # Look for the node with that label

if node is not None:

if node.left is None and node.right is None: # If it has no children

self.__reassign_nodes(node, None)

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:

tmpNode = self.get_max(

node.left

) # Gets the max value of the left branch

self.remove(tmpNode.value)

node.value = (

tmpNode.value

) # Assigns the value to the node to delete and keesp tree structure

def preorder_traverse(self, node):

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, traversalFunction=None):

"""

This function traversal the tree.

You can pass a function to traversal the tree as needed by client code

"""

if traversalFunction is None:

return self.preorder_traverse(self.root)

else:

return traversalFunction(self.root)

def postorder(curr_node):

"""

postOrder (left, right, self)

"""

nodeList = list()

if curr_node is not None:

nodeList = postorder(curr_node.left) + postorder(curr_node.right) + [curr_node]

return nodeList

def binary_search_tree():

r"""

Example

/ \

3 10

/ \ \

1 6 14

/ \ /

4 7 13

>>> t = BinarySearchTree().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

>>> BinarySearchTree().search(6)

Traceback (most recent call last):

...

IndexError: Warning: Tree is empty! please use another.

"""

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)

if t.search(6) is not None:

print("The value 6 exists")

else:

print("The value 6 doesn't exist")

if t.search(-1) is not None:

print("The value -1 exists")

else:

print("The value -1 doesn't exist")

if not t.empty():

print("Max Value: ", t.get_max().value)

print("Min Value: ", t.get_min().value)

for i in testlist:

t.remove(i)

print(t)

二叉搜索树 = binary_search_tree

if __name__ == "__main__":

import doctest

doctest.testmod()

binary_search_tree()

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