Linked list with postorder successor

Problem

Create a linked list with the nodes of a binary tree in a postorder succession.

Solution

Like the inorder successor program, a linker is used to link the linked list during post order traversal. The first found node is set to the head.

Code

public class PostorderSuccessor
{

 public static void main(String[] args)
 {
  NextNode a=new NextNode(1);
  NextNode b=new NextNode(2);
  NextNode c=new NextNode(3);
  NextNode d=new NextNode(4);
  NextNode e=new NextNode(5);
  NextNode f=new NextNode(6);
  NextNode g=new NextNode(7);
  NextNode h=new NextNode(8);
  NextNode i=new NextNode(9);
  a.left=b;
  a.right=c;
  b.right=d;
  c.left=e;
  c.right=f;
  d.left=g;
  d.right=h;
  g.right=i;
  NextNode head=linkPostorderSuccessor(a);
  while(head!=null)
  {
   System.out.println(head.value);
   head=head.next;
  }

 }
 
 public static NextNode linkPostorderSuccessor(
  NextNode root)
 {
  NodeContainer linker=new NodeContainer();
  NodeContainer head=new NodeContainer();
  linkPostorderSuccessor(root, linker, head);
  return head.node;
 }
 
 private static void linkPostorderSuccessor(
  NextNode root, NodeContainer linker, NodeContainer head)
 {
  if(root==null)
   return;
  linkPostorderSuccessor(root.left,linker,head);
  linkPostorderSuccessor(root.right, linker, head);
  if(head.node==null&&root!=null)
   head.node=root;
  if(linker.node!=null)
   linker.node.next=root;
  linker.node=root;
  
 }

}

class NextNode
{
 public NextNode left;
 public NextNode right;
 public NextNode next;
 public int value;
 public NextNode(int value)
 {
  this.value=value;
 }
}

class NodeContainer
{
 public NextNode node;
}