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.

Thoughts:

recursive DFS is more clean and easy to understand in this case, 

Code

/**
* 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)
{
if(root == null) return 0; // the Base Case is when the left/right child = null 
return 1 + Math.max(maxDepth(root.left), maxDepth(root.right));  // Key point: perform DFS, till there's no left/right child, for                                                                                                  each level we dig further into, plus one to indicate the level                                                                                                  of the recursion/tree, and compare each route recursively                                                                                                     to return the maximum depth
}
}