bsTree.py

#  https://www.geeksforgeeks.org/binary-search-tree-set-2-delete/
# A Binary Tree Node
# COPIED
class Node:
    # Constructor to create a new node
    def __init__(self, key):
        self.key = key 
        self.left = None
        self.right = None
# A utility function to do inorder traversal of BST
def inorder(root):
    if root is not None:
        inorder(root.left)
        print(root.key)
        inorder(root.right)
# A utility function to insert a new node with given key in BST
def insert( node, key): 
    # If the tree is empty, return a new node
    if node is None:
        return Node(key) 
    # Otherwise recur down the tree
    if key < node.key:
        node.left = insert(node.left, key)
    else:
        node.right = insert(node.right, key) 
    # return the (unchanged) node pointer
    return node 
# Given a non-empty binary search tree, return the node
# with minum key value found in that tree. Note that the
# entire tree does not need to be searched 
def minValueNode( node):
    current = node
    # loop down to find the leftmost leaf
    while(current.left is not None):
        current = current.left 
    return current 
# Given a binary search tree and a key, this function
# delete the key and returns the new root
def deleteNode(root, key):
    # Base Case
    if root is None:
        return root 
    # If the key to be deleted is smaller than the root's
    # key then it lies in  left subtree
    if key < root.key:
        root.left = deleteNode(root.left, key)
    # If the kye to be delete is greater than the root's key
    # then it lies in right subtree
    elif(key > root.key):
        root.right = deleteNode(root.right, key)
    # If key is same as root's key, then this is the node
    # to be deleted
    else:       
        # Node with only one child or no child
        if root.left is None :
            temp = root.right 
            root = None
            return temp 
             
        elif root.right is None :
            temp = root.left 
            root = None
            return temp
        # Node with two children: Get the inorder successor
        # (smallest in the right subtree)
        temp = minValueNode(root.right)
        # Copy the inorder successor's content to this node
        root.key = temp.key
        # Delete the inorder successor
        root.right = deleteNode(root.right , temp.key)
    return root 
# Driver program to test above functions
""" Let us create following BST
              50
           /     \
          30      70
         /  \    /  \
       20   40  60   80 """
 
root = None
root = insert(root, 50)
root = insert(root, 30)
root = insert(root, 20)
root = insert(root, 40)
root = insert(root, 70)
root = insert(root, 60)
root = insert(root, 80)
 
print ("Inorder traversal of the given tree")
inorder(root)
 
print("\nDelete 20")
root = deleteNode(root, 20)
print("Inorder traversal of the modified tree")
inorder(root)
 
print("\nDelete 30")
root = deleteNode(root, 30)
print("Inorder traversal of the modified tree")
inorder(root)
 
print("\nDelete 50")
root = deleteNode(root, 50)
print("Inorder traversal of the modified tree")
inorder(root)