From 59d17ea08d37ab5e85cae19c472686fa0a4d4a69 Mon Sep 17 00:00:00 2001
From: fw_qaq <82551626+Jack-Zhang-1314@users.noreply.github.com>
Date: Sun, 20 Nov 2022 16:39:42 +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 | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/problems/0404.左叶子之和.md b/problems/0404.左叶子之和.md
index 3118b7c0..f5b9ca39 100644
--- a/problems/0404.左叶子之和.md
+++ b/problems/0404.左叶子之和.md
@@ -600,6 +600,33 @@ impl Solution {
 }
 ```
 
+**迭代：**
+
+```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;
+        let mut stack = vec![root];
+        while !stack.is_empty() {
+            if let Some(node) = stack.pop().unwrap() {
+                if let Some(left) = &node.borrow().left {
+                    if left.borrow().left.is_none() && left.borrow().right.is_none() {
+                        res += left.borrow().val;
+                    }
+                    stack.push(Some(left.to_owned()));
+                }
+                if let Some(right) = &node.borrow().right {
+                    stack.push(Some(right.to_owned()));
+                }
+            }
+        }
+        res
+    }
+}
+```
+
 <p align="center">
 <a href="https://programmercarl.com/other/kstar.html" target="_blank">
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