LeetCode in Kotlin
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, 104]. 1 <= Node.val <= 100
Solution
import com_github_leetcode.TreeNode
/*
* Example:
* var ti = TreeNode(5)
* var v = ti.`val`
* Definition for a binary tree node.
* class TreeNode(var `val`: Int) {
* var left: TreeNode? = null
* var right: TreeNode? = null
* }
*/
@Suppress("NAME_SHADOWING")
class Solution {
fun sumEvenGrandparent(root: TreeNode?): Int {
return if (root == null) {
0
} else {
dfs(root, root.left, 0) + dfs(root, root.right, 0)
}
}
private fun dfs(grandparent: TreeNode?, parent: TreeNode?, sum: Int): Int {
var sum = sum
if (grandparent == null || parent == null) {
return sum
}
if (grandparent.`val` % 2 == 0 && parent.left != null) {
sum += parent.left!!.`val`
}
if (grandparent.`val` % 2 == 0 && parent.right != null) {
sum += parent.right!!.`val`
}
sum = dfs(parent, parent.left, sum)
sum = dfs(parent, parent.right, sum)
return sum
}
}