Medium

Quiz

#538 Convert BST to Greater Tree

APPROACH

Given the root of a Binary Search Tree (BST), transform it into a Greater Sum Tree: replace every node's value with the sum of its original value plus all BST values that are strictly greater than it. Return the modified tree.

Recall the BST property:
- The left subtree of each node holds values strictly smaller than the node.
- The right subtree holds values strictly larger.
- Both subtrees are also valid BSTs.

Example 1:

Input: root = [4,1,6,0,2,5,7,null,null,null,3,null,null,null,8]

Output: [30,36,21,36,35,26,15,null,null,null,33,null,null,null,8]

Example 2:

Input: root = [0,null,1]

Output: [1,null,1]

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What is the optimal approach for this problem?