700_search_in_a_binary_search_tree.md

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: []

Solution

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 is None:
            return None
        if root.val == val:
            return root
        elif val > root.val:
            return self.searchBST(root.right, val)
        else:
            return self.searchBST(root.left, val)