Flatten a multilevel linked list through Collection framework - data-structures

Question

Consider this example http://www.geeksforgeeks.org/flatten-a-linked-list-with-next-and-child-pointers/
I am able to flatten a multilevel linked list by collections in java but I am not able to establish relationship between a given node and its child node and next node . In the current example 10 has a child nodes with value 4,20 and 13 . I want to use Collections framework in a better way that can specify the child nodes and next nodes and then apply the flatten operation on given input. Please help me .
List<List<Integer>> obj =new LinkedList<List<Integer>>();
obj.add(Arrays.asList(10,5,12,7,11));
obj.add(Arrays.asList(4,20,13,17,6));
obj.add(Arrays.asList(2,16,9,8));
obj.add(Arrays.asList(3,19,15));
obj.stream().flatMap(e->e.stream()).forEach(i->System.out.print(i+" "));;

Answer 1

I solved the problem here is the code .
import java.util.*;
import java.lang.*;
import java.io.*;
class Node {
int data;
List<Node> child;
public Node(int data, List<Node> child) {
this.data = data;
this.child = child;
}
#Override
public String toString() {
return data+" ";
}
}
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
public static void main (String[] args) throws java.lang.Exception
{
List<Node> obj1 = new LinkedList<Node>();
obj1.add(new Node(10, Arrays.asList(new Node(4,null),new Node(20,Arrays.asList(new Node(2, null))),
new Node(13,Arrays.asList(new Node(16, Arrays.asList(new Node(3, null))))) )));
obj1.add(new Node(5, null));
obj1.add(new Node(12,null));
obj1.add(new Node(7,Arrays.asList(new Node(17, Arrays.asList(new Node(9, Arrays.asList(new Node(19, null),
new Node(15, null))),new Node(8, null))
),new Node(6, null))
));
obj1.add(new Node(11,null));
int tail=obj1.size();
for(int i=0;i<tail;i++)
{
Node n=obj1.get(i);
if(n.child!=null)
{
for(Node o:n.child)
{
obj1.add(tail, o);
tail++;
}
n.child=null;
}
}
System.out.println(obj1);
}
}