[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;
}

}

};