[:solved] 251

Author: ppxyn1

validate-binary-search-tree/ppxyn1.py

@@ -0,0 +1,20 @@
+# idea: -
+# # 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 isValidBST(self, root: Optional[TreeNode]) -> bool:
+        def dfs(node, low, high):
+            if not node:
+                return True
+            if not (low < node.val  < high):
+                return False
+            return dfs(node.left, low, node.val) and dfs(node.right, node.val, high)
+        return dfs(root, float('-inf'), float('inf'))
+    
+
+    
+