LEETCODE: 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

所见即所得！！！

/** * 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) {        while(root != NULL) {            if(root->left != NULL) {                TreeNode *rightmost = root->left->right;                while(rightmost != NULL && rightmost->right != NULL) {                    rightmost = rightmost->right;                }                TreeNode *rootright = root->right;                if(rightmost == NULL) {                    rightmost = root->left;                }                root->right = root->left;                root->left = NULL;                rightmost->right = rootright;            }            root = root->right;        }    }};