关于java:给定一个二叉树将它展开为一个单链表

原题

给定一个二叉树，原地将它开展为一个单链表。

思路

代码

class Solution {    private TreeNode pre = null;public void flatten(TreeNode root) {    if (root == null)        return;    flatten(root.right);    flatten(root.left);    root.right = pre;    root.left = null;    pre = root;}}//https://leetcode-cn.com/problems/flatten-binary-tree-to-linked-list/solution/xiang-xi-tong-su-de-si-lu-fen-xi-duo-jie-fa-by--26/