validating binary search tree solutions

Author: radiantchoi

validate-binary-search-tree/radiantchoi.py

@@ -0,0 +1,21 @@
+# 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 check(self, root: Optional[TreeNode], minimum: int, maximum: int) -> bool:
+        if root is None:
+            return True
+
+        if root.val <= minimum or root.val >= maximum:
+            return False
+
+        return self.check(root.left, minimum, root.val) and self.check(root.right, root.val, maximum)
+
+    def isValidBST(self, root: Optional[TreeNode]) -> bool:
+        minimum_constraint = ((-2) ** 31) - 1
+        maximum_constraint = 2 ** 31
+
+        return self.check(root, minimum_constraint, maximum_constraint)