LeetCode 0701. Insert into a Binary Search Tree

Problem

LeetCode

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
Copy the code

You can return this binary search tree:

         4
       /   \
      2     7
     / \   /
    1   3 5
Copy the code

This tree is also valid:

5 / \ 2 / \ 1 3\4Copy the code

Constraints:

  • The number of nodes in the given tree will be between 0 and 10 ^ 4.
  • Each node will have a unique integer value from 0 to –10 ^ 8, inclusive.
  • -10^8 <= val <= 10^8
  • It’s guaranteed that val does not exist in the original BST.

The problem

Power button

Inserts the value into the binary search tree (BST) given the root node and the value in the tree to be inserted. Returns the root node of the inserted binary search tree. Ensure that no new value exists in the original binary search tree.

Note that there may be several effective ways to insert, as long as the tree remains a binary search tree after insertion. You can return any valid result.

For example,

Given a binary search tree:

    4
   / \
  2   7
 / \
1   3
Copy the code

And insert values: 5 you can return this binary search tree:

     4
   /   \
  2     7
 / \   /
1   3 5
Copy the code

Or the tree is also valid:

5 / \ 2 / \ 1 3\4Copy the code

Train of thought

Binary tree

Python3 code
# 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 insertIntoBST(self, root: TreeNode, val: int) -> TreeNode:
        # Find the empty position
        if not root:
            return TreeNode(val)
        if root.val < val:
            root.right = self.insertIntoBST(root.right, val)
        if root.val > val:
            root.left = self.insertIntoBST(root.left, val)
        return root
Copy the code

Making a link

Python