1315. Sum of Nodes with Even-Valued Grandparent
Medium
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, 10^4]. 1 <= Node.val <= 100
透過將 parent、grandparent 節點傳下去的方式判斷是否需要加到 ans
/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func sumEvenGrandparent(root *TreeNode) int {
ans := 0
var helper func(*TreeNode, *TreeNode, *TreeNode)
helper = func(node *TreeNode, parent *TreeNode, grandParent *TreeNode) {
if node == nil {
return
}
if grandParent != nil && grandParent.Val % 2 == 0 {
ans += node.Val
}
helper(node.Left, node, parent)
helper(node.Right, node, parent)
}
helper(root, nil, nil)
return ans
}