# Convert BST to Greater Tree

Given the root of a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus the sum of all keys greater than the original key in BST.

```
def convertBST(self, root):
def visit1(root):
if root:
visit1(root.left)
vals.append(root.val)
visit1(root.right)
vals = []
visit1(root)
self.s = 0
def visit2(root):
if root:
visit2(root.right)
self.s += vals.pop()
root.val = self.s
visit2(root.left)
visit2(root)
return root
```

## Related Problems

You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists into one **sorted** list. The list should be made by splicing together the nodes of the first two lists.

Return *the head of the merged linked list*.

Given the root of a binary tree, flatten the tree into a "linked list":

The "linked list" should use the same TreeNode class where the right child pointer points to the next node in the list and the left child pointer is always null.

The "linked list" should be in the same order as a pre-order traversal of the binary tree.

Given a binary tree, determine if it is **height-balanced**.

Given the root of a binary tree, return *the length of the ***diameter*** of the tree*.

The **diameter** of a binary tree is the **length** of the longest path between any two nodes in a tree. This path may or may not pass through the root.

The **length** of a path between two nodes is represented by the number of edges between them.