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yyyyyyyyyKim.py

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# 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 invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:

# 이진트리 뒤집기(좌우반전)

# DFS(stack이용, 시간복잡도 O(n), 공간복잡도 O(n))

if not root:

return None

stack = [root]

while stack:

# 스택 맨뒤에 있는 거 pop해서 꺼내기

node = stack.pop()

# 자식 노드 교환

node.left, node.right = node.right, node.left

# 자식 노드를 스택에 추가

if node.left:

stack.append(node.left)

if node.right:

stack.append(node.right)

return root