!!!!!!114. Flatten Binary Tree to Linked List

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

For example,
Given

         1
        /        2   5
      / \        3   4   6

The flattened tree should look like:

   1
         2
             3
                 4
                     5
                         6

========

思路:

将一个二叉树 就地 压成"链表"的结构;

!!!!!!114. Flatten Binary Tree to Linked List

原文：http://www.cnblogs.com/li-daphne/p/5618735.html