应用题-二叉树专题-二叉搜索树中的搜索
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**迭代**
```python
# 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]:
r = root
while r:
if r.val > val: r = r.left
elif r.val < val: r = r.right
else: return r
return None
```
**递归**
```python
# 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 not root: return None
if root.val == val: return root
elif root.val > val: return self.searchBST( root.left, val )
else: return self.searchBST( root.right, val )
```