Convert BST to Greater Tree

LeetCode: https://leetcode.com/problems/convert-bst-to-greater-tree/

Convert a BST so each node contains the sum of all keys greater than or equal to it.

1def convertBST(root: Optional[TreeNode]) -> Optional[TreeNode]:
2    total = 0
3    def dfs(node: Optional[TreeNode]) -> None:
4        nonlocal total
5        if not node:
6            return
7        dfs(node.right)
8        total += node.val
9        node.val = total
10        dfs(node.left)
11    dfs(root)
12    return root

Evaluate N-ary Expression Tree

Kth Smallest in BST

node

tree=[5, 2, 13]

sum=13

Step 1 / 3

Step 1:

Traverse in reverse inorder to accumulate suffix sums.

Pointers: node=2

Focus: select @ [2]

sum=13