python
递归：
# 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 root == None:
return None
else:
p = root.right
root.right = root.left
root.left = p
self.invertTree(root.left)
self.invertTree(root.right)
return root
迭代（题解中的方法）
ls.pop(i) ：将列表ls中第i位置元素取出并删除该元素
class Solution:
def invertTree(self, root: TreeNode) -> TreeNode:
if not root:
return None
#将二叉树中的节点逐层放入队列中，再迭代处理队列中的元素
queue = [root]
while queue:
tmp = queue.pop(0)
tmp.left,tmp.right = tmp.right,tmp.left
if tmp.left:
queue.append(tmp.left)
if tmp.right:
queue.append(tmp.right)
return root
