[LeetCode 6.15] Search in a Binary Search Tree

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本文介绍了一种在二叉搜索树中查找特定值的高效算法。通过遍历树结构，当当前节点的值等于目标值时返回该节点，否则根据目标值与当前节点值的比较结果，决定向左子树或右子树继续搜索。若找不到匹配节点，则返回空。此方法适用于快速定位二叉搜索树中的元素。

Search in a Binary Search Tree

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.

Python3 Solution:

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