From 64b4a590729606a9466465a2e20f3685f9ac5d85 Mon Sep 17 00:00:00 2001
From: wjjiang <48505670+Spongecaptain@users.noreply.github.com>
Date: Tue, 10 Aug 2021 10:17:59 +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?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

添加 Go 语言迭代版本
---
 problems/0669.修剪二叉搜索树.md | 32 ++++++++++++++++++++++++++
 1 file changed, 32 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 26394eaa..c13af226 100644
--- a/problems/0669.修剪二叉搜索树.md
+++ b/problems/0669.修剪二叉搜索树.md
@@ -296,6 +296,7 @@ Go：
  *     Right *TreeNode
  * }
  */
+// 递归
 func trimBST(root *TreeNode, low int, high int) *TreeNode {
     if root==nil{
         return nil
@@ -312,6 +313,37 @@ func trimBST(root *TreeNode, low int, high int) *TreeNode {
     root.Right=trimBST(root.Right,low,high)
     return root
 }
+// 迭代
+func trimBST(root *TreeNode, low int, high int) *TreeNode {
+    if root == nil {
+        return nil
+    }
+    // 处理 root，让 root 移动到[low, high] 范围内，注意是左闭右闭
+    for root != nil && (root.Val<low||root.Val>high){
+        if root.Val < low{
+            root = root.Right
+        }else{
+            root = root.Left
+        }
+    }
+    cur := root
+    // 此时 root 已经在[low, high] 范围内，处理左孩子元素小于 low 的情况（左节点是一定小于 root.Val，因此天然小于 high）
+    for cur != nil{
+        for cur.Left!=nil && cur.Left.Val < low{
+            cur.Left = cur.Left.Right
+        }
+        cur = cur.Left
+    }
+    cur = root
+    // 此时 root 已经在[low, high] 范围内，处理右孩子大于 high 的情况
+    for cur != nil{
+        for cur.Right!=nil && cur.Right.Val > high{
+            cur.Right = cur.Right.Left
+        }
+        cur = cur.Right
+    }
+    return root
+}
 ```