Validate Binary Search Tree Solution

Author: doh6077

validate-binary-search-tree/doh6077.py

@@ -0,0 +1,10 @@
+class Solution:
+    def isValidBST(self, root: Optional[TreeNode]) -> bool:
+        def validate(node: Optional[TreeNode], low: float, high: float) -> bool:
+            if not node:
+                return True
+            if not (low < node.val < high):
+                return False
+            return (validate(node.left, low, node.val) and
+                    validate(node.right, node.val, high))
+        return validate(root, float('-inf'), float('inf'))