public void dfs(Node rt)
	  {
		  Stack<Node> s = new Stack<Node>();
		  
		  if(rt != null) s.add(rt);
		  
		  while(!s.isEmpty())
		  {
			  Node tNode = s.pop();
			  
			  System.out.print(tNode.value+" ");
			  
			  if(tNode.right!=null)
				  s.add(tNode.right);
			  
			  if(tNode.left!=null)
				  s.add(tNode.left);
		  }
	  }