diff --git a/problems/0226.翻转二叉树.md b/problems/0226.翻转二叉树.md
index 55dc3cbf..c34ca4bf 100644
--- a/problems/0226.翻转二叉树.md
+++ b/problems/0226.翻转二叉树.md
@@ -81,7 +81,7 @@ if (root == NULL) return root;
 
 3. 确定单层递归的逻辑
 
-因为是先前序遍历，所以先进行交换左右孩子节点，然后反转左子树，反转右子树。
+因为是前序遍历，所以先进行交换左右孩子节点，然后反转左子树，反转右子树。
 
 ```cpp
 swap(root->left, root->right);
@@ -348,14 +348,13 @@ class Solution:
         while stack:
             node = stack.pop()   
             node.left, node.right = node.right, node.left                   
+            if node.right:
+                stack.append(node.right)
             if node.left:
                 stack.append(node.left)
-            if node.right:
-                stack.append(node.right)  
         return root
 ```
 
-
 递归法：中序遍历：
 ```python
 # Definition for a binary tree node.
@@ -374,7 +373,7 @@ class Solution:
         return root
 ```
 
-迭代法：中序遍历：
+迭代法，伪中序遍历（结果是对的，看起来像是中序遍历，实际上它是前序遍历，只不过把中间节点处理逻辑放到了中间。还是要用'统一写法'才是真正的中序遍历）：
 ```python
 # Definition for a binary tree node.
 # class TreeNode:
@@ -386,18 +385,17 @@ class Solution:
     def invertTree(self, root: TreeNode) -> TreeNode:
         if not root:
             return None      
-        stack = [root]        
+        stack = [root]
         while stack:
-            node = stack.pop()                   
-            if node.left:
-                stack.append(node.left)
-            node.left, node.right = node.right, node.left               
-            if node.left:
-                stack.append(node.left)       
+            node = stack.pop()
+            if node.right:
+                stack.append(node.right)
+            node.left, node.right = node.right, node.left # 放到中间，依然是前序遍历
+            if node.right:
+                stack.append(node.right)
         return root
 ```
 
-
 递归法：后序遍历：
 ```python
 # Definition for a binary tree node.
@@ -416,7 +414,7 @@ class Solution:
         return root
 ```
 
-迭代法：后序遍历：
+迭代法，伪后序遍历（结果是对的，看起来像是后序遍历，实际上它是前序遍历，只不过把中间节点处理逻辑放到了最后。还是要用'统一写法'才是真正的后序遍历）：
 ```python
 # Definition for a binary tree node.
 # class TreeNode:
@@ -427,23 +425,19 @@ class Solution:
 class Solution:
     def invertTree(self, root: TreeNode) -> TreeNode:
         if not root:
-            return None      
-        stack = [root]        
+            return None
+        stack = [root]    
         while stack:
-            node = stack.pop()                   
+            node = stack.pop()
+            if node.right:
+                stack.append(node.right)
             if node.left:
                 stack.append(node.left)
-            if node.right:
-                stack.append(node.right)  
             node.left, node.right = node.right, node.left               
      
         return root
 ```
 
-
-
-
-
 迭代法：广度优先遍历（层序遍历）：
 ```python
 # Definition for a binary tree node.