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

 

 

class Solution {
public:
    void flatten(TreeNode* root) {
        if(root==NULL) 
            return;
        if(root->left)
            flatten(root->left);
        if(root->right)
            flatten(root->right);
        if(root->left)
        {
            TreeNode *temp = root->right;
            root->right = root->left;
            TreeNode *node = root->left;
            while(node->right)
            {
                node = node->right;
            }
            node->right = temp;
        }
        root->left=NULL;
    }
};