Diameter of Binary Tree

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.



/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    int maxDiametar = 0;

    public int diameterOfBinaryTree(TreeNode root) {
        if (root == null) {
            return 0;
        }

        preorder(root);

        return maxDiametar;
    }

    public void preorder(TreeNode root) {
        if (root == null) {
            return;
        }

        maxDiametar = (int)Math.max(maxDiametar,maxDistance(root.left) + maxDistance(root.right));

        preorder(root.right);
        preorder(root.left);
    }

    public int maxDistance(TreeNode root) {
        if (root == null) {
            return 0;
        }

        int left = maxDistance(root.left);
        int right = maxDistance(root.right);

        return (int)Math.max(left,right) + 1;
    }
}