Leetcoder - Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int maxDepth(TreeNode root) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(root==null) {
            return 0;
        }
        return visitNext(root, 0);
    }
 
    public int visitNext(TreeNode node, int maxDepth) {
        if(node==null) {
            return maxDepth;
        } else {
            int dL = visitNext(node.left, maxDepth+1);
            int dR = visitNext(node.right, maxDepth+1);
            return dL>dR?dL:dR;
        }
    }
}

/**
 * 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 maxDepth(TreeNode root) {
        return (root==null)? 0 : 1 + Math.max(maxDepth(root.left), maxDepth(root.right));
    }
}