输入一颗二叉搜索树，将该二叉搜索树转换成一个排序的双向链表

题目：

输入一颗二叉搜索树，将该二叉搜索树转换成一个排序的双向链表

要求不能创建人和新的结点，只能调整树中结点指针的指向

解答：

public class Solution {
    public static void main(String[] args) {
        BinaryTreeNode root=new BinaryTreeNode(10);
        BinaryTreeNode node1=new BinaryTreeNode(6);
        BinaryTreeNode node2=new BinaryTreeNode(14);
        BinaryTreeNode node3=new BinaryTreeNode(4);
        BinaryTreeNode node4=new BinaryTreeNode(8);
        BinaryTreeNode node5=new BinaryTreeNode(12);
        BinaryTreeNode node6=new BinaryTreeNode(16);
        root.setLchildNode(node1);root.setRchildNode(node2);
        node1.setLchildNode(node3);node1.setRchildNode(node4);
        node2.setLchildNode(node5);node2.setRchildNode(node6);
        BinaryTreeNode head=covert(root);

        while(head != null) {
            System.out.println(head.getData());
            head = head.getRchildNode();
        }
    }

    private static BinaryTreeNode covert(BinaryTreeNode root) {
        BinaryTreeNode lastNodeList = null;
        lastNodeList = covertNode(root, lastNodeList);

        while(lastNodeList != null && lastNodeList.getLchildNode() != null) {
            lastNodeList = lastNodeList.getLchildNode();
        }

        return lastNodeList;
    }

    private static BinaryTreeNode convertNode(BinaryTreeNode root, BinaryTreeNode lastNodeList) {
        if(root == null) {
            return null;
        }

        BinaryTreeNode current = root;
        if(current.getLchildNode() != null) {
            lastNodeList = covertNode(current.getLchildNode(), lastNodeList);
        }

        current.setLchildNode(lastNodeList);

        if(lastNodeList != null) {
            lastNodeList.setRchildNode(current);
        }

        lastNodeList = current;

        if(current.getRchildNode() != null) {
            lastNodeList = covertNode(current.getRchildNode(), lastNodeList);
        }

        return lastNodeList;
    }


}