Sum of Nodes with Even-Valued Grandparent - Solution & Explanation

This approach uses a depth-first search traversal to keep track of the current node's parent and grandparent values. If the grandparent's value is even, the node's value is added to the sum.

We initiate the DFS with the root, setting initial parent and grandparent values as null or zero.

In this code, we define a helper method dfs that takes the current node, its parent, and the grandparent node as arguments. We traverse the tree recursively, checking if the grandparent node exists and has an even value. If so, we add the current node's value to the total sum. The function returns the computed sum for all nodes valid under the given condition.

Utilizing an iterative method with breadth-first traversal (via a queue) enables level-wise examination of tree nodes. This format offers insight into parent-grandchild relations by leveraging node attributes over iteration.

This Python implementation leverages a queue to perform level-order traversal. Pairs of node, parent, grandparent are used to track lineage and compute the sum for nodes with even-valued grandparents.