Create 538. Convert BST to Greater Tree

Author: AishwaryaBarai

538. Convert BST to Greater Tree

@@ -0,0 +1,16 @@
+class Solution:
+    def convertBST(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+        total = 0
+        node = root
+        stack = []
+        while stack or node:
+            while node:
+                stack.append(node)
+                node = node.right
+            
+            node = stack.pop()
+            total += node.val
+            node.val = total
+            node = node.left
+        return root
+