Convert BST To Greater Tree is an example of null problems. In this post we will see how we can solve in Javascript.

Problem Description

Given 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 sum of all keys greater than the original key in BST.

Example:

Input: The root of a Binary Search Tree like this:

          5
        /   \
       2     13

Output: The root of a Greater Tree like this:

         18
        /   \
      20     13

Implementation: Please check the main.js snippet for the solution.  If you have different approach in mind or have any suggestion for this implementation feel free to share in the comment below. Thanks!