From d40a15eccca9212f701c4602a514168ab52fecf6 Mon Sep 17 00:00:00 2001
From: Steve2020 <841532108@qq.com>
Date: Wed, 26 Jan 2022 10:40:30 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=EF=BC=88=E4=BA=8C=E5=8F=89?=
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---
 problems/二叉树的迭代遍历.md | 55 ++++++++++++++++++++++++++++
 1 file changed, 55 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 4cb94cb5..ba38726b 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 +454,61 @@ var postorderTraversal = function(root, res = []) {
 };
 ```
 
+TypeScript:
+
+```typescript
+// 前序遍历（迭代法）
+function preorderTraversal(root: TreeNode | null): number[] {
+    if (root === null) return [];
+    let res: number[] = [];
+    let helperStack: TreeNode[] = [];
+    let curNode: TreeNode = root;
+    helperStack.push(curNode);
+    while (helperStack.length > 0) {
+        curNode = helperStack.pop()!;
+        res.push(curNode.val);
+        if (curNode.right !== null) helperStack.push(curNode.right);
+        if (curNode.left !== null) helperStack.push(curNode.left);
+    }
+    return res;
+};
+
+// 中序遍历（迭代法）
+function inorderTraversal(root: TreeNode | null): number[] {
+    let helperStack: TreeNode[] = [];
+    let res: number[] = [];
+    if (root === null) return res;
+    let curNode: TreeNode | null = root;
+    while (curNode !== null || helperStack.length > 0) {
+        if (curNode !== null) {
+            helperStack.push(curNode);
+            curNode = curNode.left;
+        } else {
+            curNode = helperStack.pop()!;
+            res.push(curNode.val);
+            curNode = curNode.right;
+        }
+    }
+    return res;
+};
+
+// 后序遍历（迭代法）
+function postorderTraversal(root: TreeNode | null): number[] {
+    let helperStack: TreeNode[] = [];
+    let res: number[] = [];
+    let curNode: TreeNode;
+    if (root === null) return res;
+    helperStack.push(root);
+    while (helperStack.length > 0) {
+        curNode = helperStack.pop()!;
+        res.push(curNode.val);
+        if (curNode.left !== null) helperStack.push(curNode.left);
+        if (curNode.right !== null) helperStack.push(curNode.right);
+    }
+    return res.reverse();
+};
+```
+
 Swift:
 
 > 迭代法前序遍历