---
tags: data_structure_python
---# Search in Binary Search Tree <img src="https://img.shields.io/badge/-easy-brightgreen">

Given the root node of a binary search tree (BST) and a value. You need to find the node in the BST that the node's value equals the given value. Return the subtree rooted with that node. If such node doesn't exist, you should return NULL.

For example,

Given the tree:
        4
       / \
      2   7
     / \
    1   3

And the value to search: 2

You should return this subtree:

      2     
     / \   
    1   3

In the example above, if we want to search the value `5`, since there is no node with value `5`, we should return `NULL`.

Note that an empty tree is represented by `NULL`, therefore you would see the expected output (serialized tree format) as `[]`, not `null`.

# 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 searchBST(self, root: TreeNode, val: int) -> TreeNode:
        if root == None:
            return root
        elif root.val == val:
            return root
        else:
            if val < root.val:
                return self.searchBST(root.left, val)
            if val > root.val:
                return self.searchBST(root.right, val)