Flatten Binary Tree to Linked List.md

Given a binary tree, flatten it to a linked list in-place.

For example, given the following tree:

    1
   / \
  2   5
 / \   \
3   4   6
The flattened tree should look like:

1
 \
  2
   \
    3
     \
      4
       \
        5
         \
          6

My code:

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def flatten(self, root):
        """
        :type root: TreeNode
        :rtype: None Do not return anything, modify root in-place instead.
        """
        if root==None:
            return root
        root0=root
        value_list=[]
        value_list=self.Left_first(root,value_list)
        print(value_list)
        for i,value in enumerate(value_list):
            if i==0:
                continue
            treenode=TreeNode(value)
            root0.right=treenode
            root0.left=None
            root0=treenode
        
            
    def Left_first(self,root,value_list):
        if root==None:
            return None
        value_list.append(root.val)
        left=root.left
        self.Left_first(left,value_list)
        right=root.right
        self.Left_first(right,value_list)
        return value_list
        

Solution: https://leetcode.com/problems/flatten-binary-tree-to-linked-list/