Convert binary tree to its Sum tree

Objective: Given a binary tree, write an algorithm to convert it into its Sum tree.

What is Sum tree: Sum tree of a binary tree, is a tree where each node in the converted tree will contains the sum of the left and right sub trees in the original tree.

Example:

Approach:

1. Recursively calculate the left sum from left sum tree.
2. Recursively calculate the right sum from right tree.
3. prepare the return root.data + left sum + right sum.
4. Update the root data as root.data = left sum + right sum.
5. update the newRoot = root.
6. See the code for better understanding.

Complete Code:

Output:

Original Tree: -2  -1  4  5  -6  3  10
Sum tree: 0  2  0  8  0  4  0