Leetcode147: 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

/**
* Definition for a binary tree node.
* 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)
{
if(root->left)
{
TreeNode* node = root->left;
while(node->right)
{
node = node->right;
}
node->right = root->right ;
root->right = root->left;
root->left = NULL;
}
root = root->right;
}
}
};