98. Validate Binary Search Tree

Author: amitbansal7

validate-binary-search-tree.scala

@@ -0,0 +1,12 @@
+//Runtime: 516 ms
+object Solution {
+    def isValidBST(root: TreeNode): Boolean = {
+        def solve(root:TreeNode, a:TreeNode, b:TreeNode): Boolean = root match {
+            case null => true
+            case t:TreeNode =>
+                if((a != null && root.value <= a.value) || (b != null && root.value >= b.value)) false
+                else solve(root.left, a, root) && solve(root.right, root, b)
+        }
+        solve(root, null, null)
+    }
+}