Create 98-Validate-Binary-Search-Tree.py

Author: neetcode-gh

98-Validate-Binary-Search-Tree.py

@@ -0,0 +1,19 @@
+# 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: TreeNode) -> bool:
+        
+        def valid(node, left, right):
+            if not node:
+                return True
+            if not (node.val < right and node.val > left):
+                return False
+            
+            return (valid(node.left, left, node.val) and
+                    valid(node.right, node.val, right))
+        
+        return valid(root, float("-inf"), float("inf"))