LeetCode-in-Scala.github.io
543. Diameter of Binary Tree
Easy
Given the root of a binary tree, return the length of the diameter of the tree.
The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.
The length of a path between two nodes is represented by the number of edges between them.
Example 1:
Input: root = [1,2,3,4,5]
Output: 3
Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].
Example 2:
Input: root = [1,2]
Output: 1
Constraints:
- The number of nodes in the tree is in the range
[1, 104]. -100 <= Node.val <= 100
Solution
import com_github_leetcode.TreeNode
/*
* Definition for a binary tree node.
* class TreeNode(_value: Int = 0, _left: TreeNode = null, _right: TreeNode = null) {
* var value: Int = _value
* var left: TreeNode = _left
* var right: TreeNode = _right
* }
*/
object Solution {
private var diameter: Int = 0
def diameterOfBinaryTree(root: TreeNode): Int = {
diameter = 0
diameterOfBinaryTreeUtil(root)
diameter
}
private def diameterOfBinaryTreeUtil(root: TreeNode): Int = {
if (root == null) {
return 0
}
val leftLength = if (root.left != null) 1 + diameterOfBinaryTreeUtil(root.left) else 0
val rightLength = if (root.right != null) 1 + diameterOfBinaryTreeUtil(root.right) else 0
diameter = Math.max(diameter, leftLength + rightLength)
Math.max(leftLength, rightLength)
}
}