题解 | #判断是不是二叉搜索树#

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    def isValidBST(self, root: TreeNode) -> bool:
        def inOrder(node, traversed=[]):
            if node.left:
                inOrder(node.left, traversed)
            traversed.append(node.val)
            if node.right:
                inOrder(node.right, traversed)
            return traversed

        trav = inOrder(root)
        return trav == sorted(trav)