java实现二叉树前序搜索输出深度完整代码

import java.util.Scanner;
// 1:无需package
// 2: 类名必须Main, 不可修改
class TreeNode {
    public int val;
    public TreeNode left;
    public TreeNode right;

    public TreeNode(int val){
        this.val=val;
        this.left=null;
        this.right=null;
    }
}

public class Main {
    public static void main(String[] args) {
        TreeNode root = new TreeNode(1);
        root.left = new TreeNode(2);
        root.right = new TreeNode(3);
        root.left.left = new TreeNode(4);
        root.left.right = new TreeNode(5);
         // don't forget to initialize answer before call maximum_depth
        answer=1;
        maximum(root,1);
        System.out.println("Maximum depth: " + answer);
        }
    private static int answer;
    private static void maximum(TreeNode root, int depth){
        if (root == null) {
            return;
        }
        if (root.left == null && root.right == null) {
            answer = Math.max(answer, depth);
        }

        maximum(root.left, depth + 1);
        maximum(root.right, depth + 1);}
    }