如何搜索二叉树转换为双向链表

public static class Node{
	public int value;
	public Node left;
	public Node right;
	public Node(int data){
		this.value = data;
	}
}
public static Node convert1(Node head){
	Queue<Node> queue = new LinkedList<Node>();
	inOrderToQueue(head, queue);
	if(queue.isEmpty()){
		return head;
	}
	head = queue.poll();
	Node pre = head;
	pre.left = null;
	Node cur = null;
	while(!queue.isEmpty()){
		cur = queue.poll();
		pre.right = cur;
		cur.left = pre;
		pre = cur;
	}
	pre.right = null;
	return head;
}
public static void inOrderToQueue(Node head, Queue<Node> queue){
	if(head == null){
		return;
	}
	inOrderToQueue(head.left, queue);
	queue.offer(head);
	inOrderToQueue(head.right, queue);
}

public static Node convert2(Node head){
	if(head == null){
		return null;
	}
	Node last = process(head);
	head = last.right;
	last.right = null;
	return head;
}
public static Node process(Node head){
	if(head == null){
		return null;
	}
	Node leftE = process(head.left);		//left end
	Node rightE = process(head.right);		//right end
	Node leftS = leftE != null ? leftE.right : null;	//left start
	Node rightS == rightS != null ? rightE.right : null; //right start
	if(leftE != null && rightE != null){
		leftE.right = head;
		head.left = leftE;
		head.right = rightS;
		rightS.left = head;
		rightE.right = leftS;
		return rightE;
	}else if(leftE != null){
		leftE.right = head;
		head.left = leftE;
		head.right = leftS;
		return head;
	}else if(rightE != null){
		head.right = rightS;
		rightS.left = head;
		rightE.right = head;
		return rightE;
	}else{
		head.right = head;
		return head;
	}
}