701 Insert into a Binary Search Tree.py

#!/usr/bin/python3
"""
Given the root node of a binary search tree (BST) and a value to be inserted
into the tree, insert the value into the BST. Return the root node of the BST
after the insertion. It is guaranteed that the new value does not exist in the
original BST.

Note that there may exist multiple valid ways for the insertion, as long as the
tree remains a BST after insertion. You can return any of them.

For example,

Given the tree:
        4
       / \
      2   7
     / \
    1   3
And the value to insert: 5
You can return this binary search tree:

         4
       /   \
      2     7
     / \   /
    1   3 5
This tree is also valid:

         5
       /   \
      2     7
     / \
    1   3
         \
          4
"""
# Definition for a binary tree node.
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None


class Solution:
    def insertIntoBST(self, root: TreeNode, val: int) -> TreeNode:
        if not root:
            return TreeNode(val)

        if root.val < val:
            root.right = self.insertIntoBST(root.right, val)
        elif root.val > val:
            root.left = self.insertIntoBST(root.left, val)
        else:
            raise

        return root