技術標籤：Pythonleetcode

題目：
翻轉一棵二叉樹。

思路：

解答：
法一：

# 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: TreeNode) ->
 
 TreeNode:
        if not root:
            return root
        stack=[root]
        while stack:
            cur=stack.pop()
            if cur.left:
                stack.append(cur.left)
            if cur.right:
                stack.append(cur.right)
            cur.left,cur.right=cur.right,cur.
 
left
        return root

法二：

# 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: TreeNode) -> TreeNode:
        if
 
 not root:
            return None

        def dfs(root):
            if not root:
                return
            root.left, root.right = root.right, root.left
            dfs(root.left)
            dfs(root.right)

        dfs(root) 

        return root