LeetCode in Kotlin
2641. Cousins in Binary Tree II
Medium
Given the root of a binary tree, replace the value of each node in the tree with the sum of all its cousins’ values.
Two nodes of a binary tree are cousins if they have the same depth with different parents.
Return the root of the modified tree.
Note that the depth of a node is the number of edges in the path from the root node to it.
Example 1:
Input: root = [5,4,9,1,10,null,7]
Output: [0,0,0,7,7,null,11]
Explanation: The diagram above shows the initial binary tree and the binary tree after changing the value of each node.
- Node with value 5 does not have any cousins so its sum is 0.
- Node with value 4 does not have any cousins so its sum is 0.
- Node with value 9 does not have any cousins so its sum is 0.
- Node with value 1 has a cousin with value 7 so its sum is 7.
- Node with value 10 has a cousin with value 7 so its sum is 7.
- Node with value 7 has cousins with values 1 and 10 so its sum is 11.
Example 2:
Input: root = [3,1,2]
Output: [0,0,0]
Explanation: The diagram above shows the initial binary tree and the binary tree after changing the value of each node.
- Node with value 3 does not have any cousins so its sum is 0.
- Node with value 1 does not have any cousins so its sum is 0.
- Node with value 2 does not have any cousins so its sum is 0.
Constraints:
- The number of nodes in the tree is in the range
[1, 105]. 1 <= Node.val <= 104
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
* }
*/
class Solution {
private var horizontalSum: MutableList<Int?>? = null
private fun traverse(root: TreeNode?, depth: Int) {
if (root == null) {
return
}
if (depth < horizontalSum!!.size) {
horizontalSum!![depth] = horizontalSum!![depth]!! + root.`val`
} else {
horizontalSum!!.add(root.`val`)
}
traverse(root.left, depth + 1)
traverse(root.right, depth + 1)
}
private fun traverse1(root: TreeNode?, depth: Int) {
if (root == null) {
return
}
if (depth > 0) {
var sum = 0
if (root.left != null) {
sum += root.left!!.`val`
}
if (root.right != null) {
sum += root.right!!.`val`
}
if (root.left != null) {
root.left!!.`val` = horizontalSum!![depth + 1]!! - sum
}
if (root.right != null) {
root.right!!.`val` = horizontalSum!![depth + 1]!! - sum
}
}
traverse1(root.left, depth + 1)
traverse1(root.right, depth + 1)
}
fun replaceValueInTree(root: TreeNode?): TreeNode {
horizontalSum = ArrayList()
root!!.`val` = 0
if (root.left != null) {
root.left!!.`val` = 0
}
if (root.right != null) {
root.right!!.`val` = 0
}
traverse(root, 0)
traverse1(root, 0)
return root
}
}