Given the root of a binary search tree (BST) with possible duplicates, return the mode(s) (i.e., the most frequently occurring element) in the tree. If there are multiple modes, return them in any order.
Given the root of a binary tree, return the most frequent subtree sum. A subtree sum is the sum of all the node values in the subtree rooted at any node, including the node itself. If there is a tie, return all the subtree sums with the highest frequency.
Given the root of a Binary Search Tree (BST), convert it into a Greater Tree where every node’s value is replaced by the sum of all greater node values in the BST plus its original value.
