From cbc75c008452a9ac0de0b580a30a4a1d9ec969b5 Mon Sep 17 00:00:00 2001
From: Zehua Ren <48848908+Renzehua1998@users.noreply.github.com>
Date: Thu, 19 Jan 2023 17:47:41 +0800
Subject: [PATCH] =?UTF-8?q?Update=200669.=E4=BF=AE=E5=89=AA=E4=BA=8C?=
 =?UTF-8?q?=E5=8F=89=E6=90=9C=E7=B4=A2=E6=A0=91.md=20=E6=B7=BB=E5=8A=A0?=
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---
 problems/0669.修剪二叉搜索树.md | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/problems/0669.修剪二叉搜索树.md b/problems/0669.修剪二叉搜索树.md
index ac36509f..1fd6fce0 100644
--- a/problems/0669.修剪二叉搜索树.md
+++ b/problems/0669.修剪二叉搜索树.md
@@ -299,6 +299,32 @@ class Solution:
             return root
 ```
 
+**迭代**
+```python
+class Solution:
+    def trimBST(self, root: Optional[TreeNode], low: int, high: int) -> Optional[TreeNode]:
+        if not root: return root
+        # 处理头结点，让root移动到[L, R] 范围内，注意是左闭右开
+        while root and (root.val < low or root.val > high):
+            if root.val < low:  # 小于L往右走
+                root = root.right
+            else:  # 大于R往左走
+                root = root.left
+        # 此时root已经在[L, R] 范围内，处理左孩子元素小于L的情况
+        cur = root
+        while cur:
+            while cur.left and cur.left.val < low:
+                cur.left = cur.left.right
+            cur = cur.left
+        # 此时root已经在[L, R] 范围内，处理右孩子大于R的情况
+        cur = root
+        while cur:
+            while cur.right and cur.right.val > high:
+                cur.right = cur.right.left
+            cur = cur.right
+        return root
+```
+
 ## Go 
 
 ```go