0114-flatten-binary-tree-to-linked-list.adoc

114. Flatten Binary Tree to Linked List

{leetcode}/problems/flatten-binary-tree-to-linked-list/[LeetCode - Flatten Binary Tree to Linked List^]

Given a binary tree, flatten it to a linked list in-place.

For example, given the following tree:

    1
   / \
  2   5
 / \   \
3   4   6

The flattened tree should look like:

1
 \
  2
   \
    3
     \
      4
       \
        5
         \
          6

思路分析

这道题本质上来讲可以说是要做一个先根遍历。但是，却可以将这个过程逆向过来，从底向上建立起关联。不可谓不精巧。

思考题：看题解中，可以逐级将左树并入到右树。尝试一下。

link:{sourcedir}/_0114_FlattenBinaryTreeToLinkedList.java[role=include]

link:{sourcedir}/_0114_FlattenBinaryTreeToLinkedList_2.java[role=include]

link:{sourcedir}/_0114_FlattenBinaryTreeToLinkedList_3.java[role=include]

思考题

如何使用递归来实现？

link:{sourcedir}/_0114_FlattenBinaryTreeToLinkedList_3rec.java[role=include]

参考资料

1. 详细通俗的思路分析，多解法 - 二叉树展开为链表 - 力扣（LeetCode）

2. 114. Flatten Binary Tree to Linked List · leetcode