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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.



Convert binary tree to its Sum tree.

Con­vert binary tree to its Sum tree.


  1. Recur­sively cal­cu­late the left sum from left sum tree.
  2. Recur­sively cal­cu­late the right sum from 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 bet­ter understanding.

Com­plete Code:


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

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  • traex

    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.

    • Dev Kashyap

      I agree. Its not required at all.