LeetCode Q114: 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

Solution:
Using recursion, every time, link the right sub-tree to the deepest leaf node of the left sub-tree.

My code accepted in one pass, first time~!! Woo-Hoo~

	/**
	* 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==NULL)
	return;
	if(root->left!=NULL)
	flatten(root->left);
	if(root->right!=NULL)
	flatten(root->right);
	TreeNode* tmpRight=root->right;
	TreeNode* leftLeef;
	if(root->left==NULL)
	leftLeef=root;
	else{
	leftLeef=root->left;
	while(leftLeef->right!=NULL){
	leftLeef=leftLeef->right;
	}
	}
	if(root->left!=NULL)
	root->right=root->left;
	root->left=NULL;
	leftLeef->right=tmpRight;
	}
	};

view raw Q114FlattenBinaryTreeToLinkedList.cpp hosted with ❤ by GitHub