diff --git a/problems/0098.验证二叉搜索树.md b/problems/0098.验证二叉搜索树.md index 95ae783f..93c2272c 100644 --- a/problems/0098.验证二叉搜索树.md +++ b/problems/0098.验证二叉搜索树.md @@ -392,7 +392,26 @@ class Solution: return is_left_valid and is_right_valid return __isValidBST(root) ``` - +**递归** - 避免初始化最小值做法: +```python +class Solution: + def isValidBST(self, root: TreeNode) -> bool: + # 规律: BST的中序遍历节点数值是从小到大. + pre = None + def __isValidBST(root: TreeNode) -> bool: + nonlocal pre + + if not root: + return True + + is_left_valid = __isValidBST(root.left) + if pre and pre.val>=root.val: return False + pre = root + is_right_valid = __isValidBST(root.right) + + return is_left_valid and is_right_valid + return __isValidBST(root) +``` ```python 迭代-中序遍历 class Solution: