Week10 SLOG: mutate Insert and Delete function

In this week, I have learned something about mutating functions like insert and delete in Binary Search Tree.

First of all, I need to define class BTNode and BST. And I also need to initialize them.

class BTNode:

    '''Binary Tree node.'''

    def __init__(self, data, left=None, right=None):

        ''' (BTNode, object, BTNode, BTNode) -> NoneType

        Create BTNode (self) with data and children left and right.

        '''

        self.data, self.left, self.right = data, left, right

Class BST:

'''Binary Search Tree node.'''

def __init__(self, root=None):

    '''(BST, BTNode or None) -> Nonetype

    Create BST with BTNode root.

    '''

    Self.root = root

Next, I mutate insert and delete methods.

def insert(node, data):

    ''' (BTNode, object) -> BTNode

    Insert data in BST rooted at node if necessary, and return new root.

    >>> b = BTNode(8)

    >>> b = insert(b, 4)

    >>> b = insert(b, 2)

    >>> b = insert(b, 6)

    >>> b = insert(b, 12)

    >>> b = insert(b, 14)

    >>> b = insert(b, 10)

    >>> print(b)

            14

        12

            10

    8

            6

        4

            2

    <BLANKLINE>

    '''

    return_node = node

    if not node:

        return_node = BTNode(data)

    elif data < node.data:

        node.left = insert(node.left, data)

    elif data > node.data:

        node.right = insert(node.right, data)

    else:  # nothing to do

        pass

    return return_node

def delete(node, data):

    ''' (BTNode, data) -> BTNode

    Delete, if it exists, node with data and return resulting tree.

    >>> b = BTNode(8)

    >>> b = insert(b, 4)

    >>> b = insert(b, 2)

    >>> b = insert(b, 6)

    >>> b = insert(b, 12)

    >>> b = insert(b, 14)

    >>> b = insert(b, 10)

    >>> b = delete(b, 12)

    >>> print(b)

            14

        10

    8

            6

        4

            2

    <BLANKLINE>

    '''

    if not node:

        pass

    elif data < node.data:

        node.left = delete(node.left, data)

    elif data > node.data:

        node.right = delete(node.right, data)

    elif not node.left:

        return_node = node.right

    elif not node.right:

        return_node = node.left

    else:

        node.data = _find_max(node.left).data

        node.left = delete(node.left, node.data)

    return return_node