Insert into a Binary Search Tree — LeetCode 701 Python Solution

The problem

You are given the root node of a binary search tree (BST) and a value to insert into the tree. Return the root node of the BST after the insertion.

Example

Input

root = [4,2,7,1,3], val = 5

Output

[4,2,7,1,3,5]

Explanation

Another accepted tree is:

Python solution

# 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: Optional[TreeNode], val: int) -> Optional[TreeNode]:
        if root is None:
            return TreeNode(val)
        if root.val > val:
            root.left = self.insertIntoBST(root.left, val)
        else:
            root.right = self.insertIntoBST(root.right, val)
        return root

Complexity

Pattern: Tree Traversal

Choose the order — preorder, inorder, postorder, level — and the problem solves itself. LeetCode 701. Insert into a Binary Search Tree is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Tree, Binary Tree and Binary Search Tree.

The tree traversal guide has the Python template for the pattern and the 225 LeetCode problems that use it.

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