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 :



title-img



                        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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