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
SOLUTION:
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def sumEvenGrandparent(self, root: TreeNode) -> int:
paths = [(root, [root.val] if root else [])]
i = 0
total = 0
while i < len(paths):
curr, currpath = paths[i]
if curr:
if len(currpath) > 2 and currpath[-3] % 2 == 0:
total += curr.val
if curr.left:
paths.append((curr.left, currpath + [curr.left.val]))
if curr.right:
paths.append((curr.right, currpath + [curr.right.val]))
i += 1
return total
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