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114.二叉树展开为链表.py
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114.二叉树展开为链表.py
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#
# @lc app=leetcode.cn id=114 lang=python3
#
# [114] 二叉树展开为链表
#
# @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.
"""
preorderList = list()
# 前序遍历,结果存到preorderList
def preorderTraversal(root: TreeNode):
if root:
preorderList.append(root)
preorderTraversal(root.left)
preorderTraversal(root.right)
preorderTraversal(root)
# 节点一个个连接,形成单链表
for i in range(1, len(preorderList)):
prev, curr = preorderList[i - 1], preorderList[i]
prev.left = None
prev.right = curr
# @lc code=end