import com.google.gson.Gson;

import java.util.Comparator;
import java.util.List;

public class PerformanceTester {
    static String givenJson = "[\n" +
            "{\n" +
            "\"Title\": \"Introduction\",\n" +
            "\"Order\": 1,\n" +
            "\"DisplayNumber\": \"\",\n" +
            "\"SubCategories\": []\n" +
            "},\n" +
            "{\n" +
            "\"Title\": \"Chapter 1\",\n" +
            "\"Order\": 2,\n" +
            "\"DisplayNumber\": \"1.\",\n" +
            "\"SubCategories\": [\n" +
            "{\n" +
            "\"Title\": \"Chapter 1.1\",\n" +
            "\"Order\": 1,\n" +
            "\"DisplayNumber\": \"1.1.\",\n" +
            "\"SubCategories\": [\n" +
            "{\n" +
            "\"Title\": \"Chapter 1.1.1\",\n" +
            "\"Order\": 1,\n" +
            "\"DisplayNumber\": \"1.1.1.\",\n" +
            "\"SubCategories\": []\n" +
            "}\n" +
            "]\n" +
            "},\n" +
            "{\n" +
            "\"Title\": \"Chapter 1.2\",\n" +
            "\"Order\": 2,\n" +
            "\"DisplayNumber\": \"1.2.\",\n" +
            "\"SubCategories\": []\n" +
            "}\n" +
            "]\n" +
            "},\n" +
            "{\n" +
            "\"Title\": \"Chapter 2\",\n" +
            "\"Order\": 3,\n" +
            "\"DisplayNumber\": \"2.\",\n" +
            "\"SubCategories\": []\n" +
            "}\n" +
            "]";
    static String forWork = "{\n" +
            "\"Title\":\"root\",\n" +
            "\"Order\":1\n," +
            "\"DisplayNumber\": \"\"\n," +
            "\"SubCategories\":" + givenJson + "\n" +
            "}";

    public static void main(String[] args) throws QueueFullException {
        Node root = new Gson().fromJson(forWork, Node.class);
        dfs(root, 0);
    }

    static void dfs(Node u, int d) {
        if (!u.Title.equals("root")) {
            if (u.DisplayNumber != null && u.DisplayNumber.length() > 0) {
                System.out.print(u.DisplayNumber + " ");
            }
            System.out.println(u.Title);
        }
        u.SubCategories.sort(Comparator.comparingInt(o -> o.Order));
        for (Node v : u.SubCategories) {
            dfs(v, d + 1);
        }
    }
}

class Node {
    String Title;
    int Order;
    String DisplayNumber;
    List<Node> SubCategories;
}