114.flatten-binary-tree-to-linked-list.py

#
# @lc app=leetcode id=114 lang=python3
#
# [114] Flatten Binary Tree to Linked List
#


# @lc code=start
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def flatten(self, root: Optional[TreeNode]) -> None:
        """
        Do not return anything, modify root in-place instead.
        """
        if not root:
            return None
        stack = [root]
        while stack:
            node = stack.pop()
            if node.right:
                stack.append(node.right)
            if node.left:
                stack.append(node.left)
            if stack:
                node.right = stack[-1]
            node.left = None
        return root


# @lc code=end