**Sum of Nodes with Even Grandparent Values - Amazon Top Interview Questions**

### Problem Statement :

Given a binary tree root, return the sum of all node values whose grandparents have an even value. Constraints 0 ≤ n ≤ 100,000 where n is the number of nodes in root Example 1 Input root = [8, [4, [6, null, null], [7, null, [2, null, null]]], [3, null, null]] Output 15 Explanation Nodes 6, 7, and 2 have an even value grandparent.

### Solution :

` ````
Solution in C++ :
void traverse(Tree* current, Tree* parent, Tree* grandparent, int& count) {
if (current == NULL) return;
if (grandparent != NULL && grandparent->val % 2 == 0) {
count += current->val;
}
traverse(current->left, current, parent, count);
traverse(current->right, current, parent, count);
}
int solve(Tree* root) {
int count = 0;
traverse(root, NULL, NULL, count);
return count;
}
```

` ````
Solution in Python :
class Solution:
def solve(self, root):
s = 0
if not root:
return
q = deque([(None, None, root)])
while q:
gp, p, c = q.popleft()
if gp and gp.val % 2 == 0:
s += c.val
if c.left:
q.append((p, c, c.left))
if c.right:
q.append((p, c, c.right))
return s
```

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