From 15379361aa9b1c1c062870d9e4790ca24ae51a1b Mon Sep 17 00:00:00 2001
From: fw_qaq <82551626+Jack-Zhang-1314@users.noreply.github.com>
Date: Sun, 20 Nov 2022 16:11:25 +0800
Subject: [PATCH] =?UTF-8?q?Update=200404.=E5=B7=A6=E5=8F=B6=E5=AD=90?=
 =?UTF-8?q?=E4=B9=8B=E5=92=8C.md?=
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---
 problems/0404.左叶子之和.md | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/problems/0404.左叶子之和.md b/problems/0404.左叶子之和.md
index 6b6fe729..3118b7c0 100644
--- a/problems/0404.左叶子之和.md
+++ b/problems/0404.左叶子之和.md
@@ -575,6 +575,31 @@ object Solution {
 }
 ```
 
+### Rust
+
+**递归**
+
+```rust
+use std::cell::RefCell;
+use std::rc::Rc;
+impl Solution {
+    pub fn sum_of_left_leaves(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let mut res = 0;
+        if let Some(node) = root {
+            if let Some(left) = &node.borrow().left {
+                if left.borrow().right.is_none() && left.borrow().right.is_none() {
+                    res += left.borrow().val;
+                }
+            }
+            res + Self::sum_of_left_leaves(node.borrow().left.clone())
+                + Self::sum_of_left_leaves(node.borrow().right.clone())
+        } else {
+            0
+        }
+    }
+}
+```
+
 <p align="center">
 <a href="https://programmercarl.com/other/kstar.html" target="_blank">
   <img src="../pics/网站星球宣传海报.jpg" width="1000"/>