# 543 Diameter of Binary Tree

### Problem:

Given a binary tree, you need to compute 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.

Example: Given a binary tree

``````          1
/ \
2   3
/ \
4   5
``````

Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].

Note: The length of path between two nodes is represented by the number of edges between them.

### Solutions:

``````/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int diameterOfBinaryTree(TreeNode root) {
int[] res = new int;
res = 0;
process(root, res);
return res;
}
private int process(TreeNode node, int[] res) {
if (node == null) {
return -1;
}
int left = process(node.left, res) + 1;
int right = process(node.right, res) + 1;
res = Math.max(res, left + right);
return Math.max(left, right);
}
}
``````