Given a binary tree, the task is to print the sum of all the boundary nodes of the tree.
Input: 1 / \ 2 3 / \ / \ 4 5 6 7 Output: 28 Input: 1 / \ 2 3 \ / 4 5 \ 6 / \ 7 8 Output: 36
Approach: We have already discussed the Boundary Traversal of a Binary tree. Here we will find the sum of the boundary nodes of the given binary tree in four steps:
- Sum up all the nodes of the left boundary,
- Sum up all the leaf nodes of the left sub-tree,
- Sum up all the leaf nodes of the right sub-tree and
- Sum up all the nodes of the right boundary.
We will have to take care of one thing that nodes don’t add up again, i.e. the left most node is also the leaf node of the tree.
Below is the implementation of the above approach:
Time Complexity: O(N) where N is the number of nodes in the binary tree.
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