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As the question say, how may I create a server- client application using DatagramPacket and DatagramSocket ?

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    Please [edit] your question the actual output. Also The table is not very clear to me. Why does each node have a root value ? Node 4 is the parent of 6 but 4 is not defined in the table. What does `map` represent ? – c0der Mar 05 '20 at 16:53
  • It looks good, can you please show what exactly the output for your example code is? And have you tried with a simpler graph, like the 12345 example? – kutschkem Mar 06 '20 at 07:55
  • Please add @c0der to your message so I know you replied. Essential information should be in the post and not in comments. – c0der Mar 08 '20 at 04:58

1 Answers1

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See the following solution: 

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

public class DFSTree {

    public static ArrayList<Integer> listeIDsOrder = new ArrayList<>();

    public static void main (String[] args){
        Map<Integer, Integer> map = new HashMap<>();

        map.put (1, null);   //root
        map.put (10, 1);
        map.put (11, 10);
        map.put (12, 10);
        map.put (13, 10);

        map.put (20, 1);
        map.put (21, 20);
        map.put (22, 20);

        map.put (30, 1);
        map.put (31, 30);

        getOrder (1, map);
        System.out.println (listeIDsOrder);
    }

    public static void getOrder (int root, Map<Integer, Integer> graph){

        LinkedList<Integer> stack = new LinkedList<>(); //use stack for correct order of processing
        stack.add(root); //add root
        getOrder(graph, stack);
    }

    public static void getOrder (Map<Integer, Integer> graph, LinkedList<Integer> stack ){

        while(!stack.isEmpty()){

            int node =  stack.pollFirst(); //for bfs order. for dfs order use stack.pollLast();
            listeIDsOrder.add(node);

             List<Integer> keys = new ArrayList<>(graph.keySet());
             Collections.sort(keys);

            for(int key : keys){
                if(graph.get(key) != null && graph.get(key) == node) {
                    stack.add(key);
                }
            }
        }
    }
}

Output: [1, 10, 20, 30, 11, 12, 13, 21, 22, 31]

c0der
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