From f604aea34c6632e20ad4ced37cb24c005420e574 Mon Sep 17 00:00:00 2001
From: Steve2020 <841532108@qq.com>
Date: Tue, 8 Feb 2022 23:00:31 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=EF=BC=880404.=E5=B7=A6?=
 =?UTF-8?q?=E5=8F=B6=E5=AD=90=E4=B9=8B=E5=92=8C.md=EF=BC=89=EF=BC=9A?=
 =?UTF-8?q?=E5=A2=9E=E5=8A=A0typescript=E7=89=88=E6=9C=AC?=
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---
 problems/0404.左叶子之和.md | 44 ++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/problems/0404.左叶子之和.md b/problems/0404.左叶子之和.md
index 09272052..2b4df151 100644
--- a/problems/0404.左叶子之和.md
+++ b/problems/0404.左叶子之和.md
@@ -372,6 +372,50 @@ var sumOfLeftLeaves = function(root) {
 };
 ```
 
+## TypeScript
+
+> 递归法
+
+```typescript
+function sumOfLeftLeaves(root: TreeNode | null): number {
+    if (root === null) return 0;
+    let midVal: number = 0;
+    if (
+        root.left !== null &&
+        root.left.left === null &&
+        root.left.right === null
+    ) {
+        midVal = root.left.val;
+    }
+    let leftVal: number = sumOfLeftLeaves(root.left);
+    let rightVal: number = sumOfLeftLeaves(root.right);
+    return midVal + leftVal + rightVal;
+};
+```
+
+> 迭代法
+
+```typescript
+function sumOfLeftLeaves(root: TreeNode | null): number {
+    let helperStack: TreeNode[] = [];
+    let tempNode: TreeNode;
+    let sum: number = 0;
+    if (root !== null) helperStack.push(root);
+    while (helperStack.length > 0) {
+        tempNode = helperStack.pop()!;
+        if (
+            tempNode.left !== null &&
+            tempNode.left.left === null &&
+            tempNode.left.right === null
+        ) {
+            sum += tempNode.left.val;
+        }
+        if (tempNode.right !== null) helperStack.push(tempNode.right);
+        if (tempNode.left !== null) helperStack.push(tempNode.left);
+    }
+    return sum;
+};
+```
 
 ## Swift