【LeetCode 面试经典150题】114. Flatten Binary Tree to Linked List 二叉树展开为链表

114. Flatten Binary Tree to Linked List

题目大意

Given the root of a binary tree, flatten the tree into a “linked list”:

• The “linked list” should use the same TreeNode class where the right child pointer points to the next node in the list and the left child pointer is always null.
• The “linked list” should be in the same order as a pre-order traversal of the binary tree.

中文释义

给定一个二叉树的根节点，将树展平成一个“链表”：

• “链表”应该使用相同的 TreeNode 类，其中右子指针指向列表中的下一个节点，左子指针始终为 null。
• “链表”应该与二叉树的前序遍历顺序相同。

示例

示例 1:

输入: root = [1,2,5,3,4,null,6]
输出: [1,null,2,null,3,null,4,null,5,null,6]