Delete Node from a BST [LeetCode 450]

DeleteNodeBST.py

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    
    def deleteAndReplaceWithMin(self, root: TreeNode):
        
        # Find minimum from the right subtree
        curr = root.right
        while curr.left:
            curr = curr.left

        # Remove the current from right subtree
        root.right = self.deleteNode(root.right, curr.val)

        # Replace the root val
        root.val = curr.val
        
        return
    
    def deleteAndReplaceWithMax(self, root: TreeNode):
        
        # Find maximum from the left subtree
        curr = root.left
        while curr.right:
            curr = curr.right

        # Remove the current from left subtree
        root.left = self.deleteNode(root.left, curr.val)

        # Replace the root val
        root.val = curr.val
        
        return
    
    def deleteNode(self, root: Optional[TreeNode], key: int) -> Optional[TreeNode]:
        if root:
            if key < root.val:
                root.left = self.deleteNode(root.left, key)
            elif key > root.val:
                root.right = self.deleteNode(root.right, key)
            else:
                # Remove leaf and nothing changes
                if not root.left and not root.right:
                    root = None
                # Remove a node with only one child, in this point the parent of node to that child
                elif not root.left:
                    root = root.right
                elif not root.right:
                    root = root.left
                # Remove a node with two children, either replace the node with minimum from right
                # subtree or replace the node with maximum of left subtree.
                else:
                    self.deleteAndReplaceWithMin(root) # self.deleteAndReplaceWithMax(root)
                    
        return root