Update 0226.翻转二叉树.md

problems/0226.翻转二叉树.md

@@ -230,6 +230,56 @@ class Solution {
 
 Python：
 
+> 递归法：前序遍历
+```python
+class Solution:
+    def invertTree(self, root: TreeNode) -> TreeNode:
+        if not root:
+            return None
+        root.left, root.right = root.right, root.left #中
+        self.invertTree(root.left) #左
+        self.invertTree(root.right) #右
+        return root
+```
+
+> 迭代法：深度优先遍历（前序遍历）
+```python
+class Solution:
+    def invertTree(self, root: TreeNode) -> TreeNode:
+        if not root:
+            return root
+        st = []
+        st.append(root)
+        while st:
+            node = st.pop()
+            node.left, node.right = node.right, node.left #中
+            if node.right:
+                st.append(node.right) #右
+            if node.left:
+                st.append(node.left) #左
+        return root
+```
+
+> 迭代法：广度优先遍历（层序遍历）
+```python
+import collections
+class Solution:
+    def invertTree(self, root: TreeNode) -> TreeNode:
+        queue = collections.deque() #使用deque()
+        if root:
+            queue.append(root)
+        while queue:
+            size = len(queue)
+            for i in range(size):
+                node = queue.popleft()
+                node.left, node.right = node.right, node.left #节点处理
+                if node.left:
+                    queue.append(node.left)
+                if node.right:
+                    queue.append(node.right)
+        return root
+```
+
 Go：
 ```Go
 func invertTree(root *TreeNode) *TreeNode {