Convert binary tree to its Sum tree

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

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


Convert binary tree to its Sum tree.


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



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

2 thoughts on “Convert binary tree to its Sum tree”

  1. why do u need to set the newRoot in line13? you are not changing any node pointers in the SumTree method. looks like an unnecessary line of code that really does nothing.


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