JZ38 二叉树的深度

https://www.nowcoder.com/practice/435fb86331474282a3499955f0a41e8b

import java.lang.Math;

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    public int TreeDepth(TreeNode root) {
        return dfs(root, 0);
    }
    
    public int dfs(TreeNode root, int num) {
        if (root == null) return num;
        
        return Math.max(
             dfs(root.left, num + 1),
             dfs(root.right, num + 1)
        );
    }
}