二叉搜索树与双向链表

import java.util.Vector;class TreeNode { int val = 0; TreeNode left = null; TreeNode right = null; public TreeNode(int val) { this.val = val; } }public class Solution {    private Vector<TreeNode> treeNodeVector =            new Vector<>();    public TreeNode Convert(TreeNode pRootOfTree) {        Find(pRootOfTree);        for(int i = 0; i < treeNodeVector.size(); ++i) {            if(i != treeNodeVector.size()-1) {                TreeNode first = treeNodeVector.get(i);                TreeNode second = treeNodeVector.get(i+1);                first.right = second;                second.left = first;            }        }        return treeNodeVector.size() == 0 ? null : treeNodeVector.get(0);    }    public void Find(TreeNode treeNode) {        if(treeNode == null) return;        Find(treeNode.left);        treeNodeVector.add(treeNode);        Find(treeNode.right);    }}