LeetCode-in-Dart
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
/**
* Definition for a binary tree node.
* class TreeNode {
* int val;
* TreeNode? left;
* TreeNode? right;
* TreeNode([this.val = 0, this.left, this.right]);
* }
*/
class Solution {
int diameter = 0;
int diameterOfBinaryTree(TreeNode? root) {
diameter = 0;
_diameterOfBinaryTreeUtil(root);
return diameter;
}
int _diameterOfBinaryTreeUtil(TreeNode? root) {
if (root == null) {
return 0;
}
int leftLength = root.left != null ? 1 + _diameterOfBinaryTreeUtil(root.left) : 0;
int rightLength = root.right != null ? 1 + _diameterOfBinaryTreeUtil(root.right) : 0;
diameter = diameter > (leftLength + rightLength) ? diameter : (leftLength + rightLength);
return leftLength > rightLength ? leftLength : rightLength;
}
}