二叉树的高度

import java.util.*;
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) {
        if(root == null) return 0;
        else return 1 + Math.max(TreeDepth(root.left), TreeDepth(root.right));
    }
}