Find the maximum depth of a binary tree using depth-first search

maxDepthOfBTree.java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public int maxDepth(TreeNode root) {
    int depth = 0; 
    if(root == null) 
        return depth; 
        
    int lDepth = maxDepth(root.left); 
    int rDepth = maxDepth(root.right); 
    return 1 + Math.max(lDepth, rDepth);  
}