Leetcode-98.验证二叉搜索树（Python）

题目链接

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class Solution:
    def isValidBST(self, root: Optional[TreeNode]) -> bool:
        return self.isValidBSTHelper(root, float('-inf'), float('inf'))

    def isValidBSTHelper(self, root, min_val, max_val):
        if not root:
            return True
        if root.val <= min_val or root.val >= max_val:
            return False
        left_valid = self.isValidBSTHelper(root.left, min_val, root.val)
        right_valid = self.isValidBSTHelper(root.right, root.val, max_val)
        return left_valid and right_valid