Link: https://leetcode.cn/problems/diameter-of-binary-tree/
Question
difficulty: mid
adj diff: 4
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
只需要借助一个 helper function 来 return depth就行了。
Code
class Solution {
int max = 0;
public int diameterOfBinaryTree(TreeNode root) {
depth(root);
return max - 1;
}
private int depth(TreeNode node) {
if (node == null) return 0;
int ll = depth(node.left);
int rr = depth(node.right);
max = Math.max(max, ll + 1 + rr);
return Math.max(ll, rr) + 1;
}
}