[leetcode 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root的右子树接在root左子树的最右孩子的右侧，以此交换

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    void flatten(TreeNode *root) {        if (!root) {            return ;        }        while (root) {            auto tmp = root->left;            if (tmp) {                while (tmp->right) {                    tmp = tmp->right;                }                tmp->right = root->right;                root->right = root->left;                root->left = NULL;            }            root = root->right;        }            }};