From 2e877cf1e838dbfd1d48b9a61d62562d14bcb592 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=9E=81=E5=AE=A2=E5=AD=A6=E4=BC=9F?= <qxuewei@yeah.net>
Date: Mon, 27 Dec 2021 18:47:28 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20=E4=BA=8C=E5=8F=89?=
 =?UTF-8?q?=E6=A0=91=E7=9A=84=E8=BF=AD=E4=BB=A3=E9=81=8D=E5=8E=86=20Swift?=
 =?UTF-8?q?=E7=89=88=E6=9C=AC?=
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---
 problems/二叉树的迭代遍历.md | 73 ++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/problems/二叉树的迭代遍历.md b/problems/二叉树的迭代遍历.md
index a139652c..4cb94cb5 100644
--- a/problems/二叉树的迭代遍历.md
+++ b/problems/二叉树的迭代遍历.md
@@ -454,6 +454,79 @@ var postorderTraversal = function(root, res = []) {
 };
 ```
 
+Swift:
+
+> 迭代法前序遍历
+```swift
+func preorderTraversal(_ root: TreeNode?) -> [Int] {
+    var res = [Int]()
+    if root == nil {
+        return res
+    }
+    var stack = [TreeNode]()
+    stack.append(root!)
+    while !stack.isEmpty {
+        let node = stack.popLast()!
+        res.append(node.val)
+        if node.right != nil {
+            stack.append(node.right!)
+        }
+        if node.left != nil {
+            stack.append(node.left!)
+        }
+    }
+    return res
+}
+```
+
+> 迭代法中序遍历
+```swift
+func inorderTraversal(_ root: TreeNode?) -> [Int] {
+    var res = [Int]()
+    if root == nil {
+        return res
+    }
+    var stack = [TreeNode]()
+    var cur: TreeNode? = root
+    while cur != nil || !stack.isEmpty {
+        if cur != nil {
+            stack.append(cur!)
+            cur = cur!.left
+        } else {
+            cur = stack.popLast()
+            res.append(cur!.val)
+            cur = cur!.right
+        }
+    }
+    return res
+}
+```
+
+> 迭代法后序遍历
+```swift
+func postorderTraversal(_ root: TreeNode?) -> [Int] {
+    var res = [Int]()
+    if root == nil {
+        return res
+    }
+    var stack = [TreeNode]()
+    stack.append(root!)
+    // res 存储 中 -> 右 -> 左
+    while !stack.isEmpty {
+        let node = stack.popLast()!
+        res.append(node.val)
+        if node.left != nil  {
+            stack.append(node.left!)
+        }
+        if node.right != nil  {
+            stack.append(node.right!)
+        }
+    }
+    // res 翻转
+    res.reverse()
+    return res
+}
+```
 
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 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>