1315. Sum of Nodes with Even-Valued Grandparent

https://leetcode.com/problems/sum-of-nodes-with-even-valued-grandparent

Description

Given the root of a binary tree, return the sum of values of nodes with an even-valued grandparent. If there are no nodes with an even-valued grandparent, return 0.

A grandparent of a node is the parent of its parent if it exists.

Example 1:

**Input:** root = [6,7,8,2,7,1,3,9,null,1,4,null,null,null,5]
**Output:** 18
**Explanation:** The red nodes are the nodes with even-value grandparent while the blue nodes are the even-value grandparents.

Example 2:

**Input:** root = [1]
**Output:** 0

Constraints:

• The number of nodes in the tree is in the range [1, 104].

• 1 <= Node.val <= 100

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