# [leetcode] 700. Search in a Binary Search Tree _ Algorithm Problem Solve for python

## 1. Problem

700. Search in a Binary Search Tree

You are given the root of a binary search tree (BST) and an integer val.

Find the node in the BST that the node’s value equals val and return the subtree rooted with that node. If such a node does not exist, return null.

Example 1:

Input: root = [4,2,7,1,3], val = 2
Output: [2,1,3]


Example 2:

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


Constraints:

• The number of nodes in the tree is in the range [1, 5000].
• 1 <= Node.val <= 10^7
• root is a binary search tree.
• 1 <= val <= 10^7

## 2. Solution

I solved this problem like this.

• Complexity
• Time complexity : O(logN)
• Space complexity : O(1)
• Step
• Using recursive function
# 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: Optional[TreeNode], val: int) -> Optional[TreeNode]:
if root == None:
return None
if val == root.val:
return root
if val < root.val:
return self.searchBST(root.left, val)
else:
return self.searchBST(root.right, val)