leetcode-python-验证二叉搜索树

中序遍历递归写法

思考良久写不出来，借鉴了网上的写法

# 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 validBST(self,root,small,large):
        if root==None:
            return True
        if small>=root.val or large<=root.val:
            return False  
        return self.validBST(root.left,small,root.val) and self.validBST(root.right,root.val,large)

    def isValidBST(self, root: TreeNode) -> bool:
        return self.validBST(root,-2**32,2**32-1)