diff --git a/validate-bintree.py b/validate-bintree.py
new file mode 100644
index 0000000..3df471c
--- /dev/null
+++ b/validate-bintree.py
@@ -0,0 +1,19 @@
+class Solution:
+    def isValidBST(self, root: Optional[TreeNode]) -> bool:
+        return self.traverse(root, [], [])
+
+    def traverse(self, root: Optional[TreeNode], gt: List[int], lt: List[int]) -> bool:
+        left = True
+        right = True
+        for item in lt:
+            if root.val >= item:
+                return False
+        for item in gt:
+            if root.val <= item:
+                return False
+
+        if root.left != None:
+            left = self.traverse(root.left, gt, lt + [root.val])
+        if root.right != None:
+            right = self.traverse(root.right, gt + [root.val], lt)
+        return left and right